added 'jvm_arg' option for jar-tool config in pants.ini
added 'jvm_arg' option for jar-tool config in pants.ini

This does not solve issue 169, but it makes is less painful and easier to configure/diagnose.

Testing Done:
Added this to pants.ini:

[jar-tool]
jvm_args:['-Xmx257M']

I used '257' because its an unlikely value.

PANTS_DEV=1 ./pants goal ng-killall
PANTS_DEV=1 ./pants goal bundle <target>

ps auxww | grep 257M shows the NGServer process.

Bugs closed: 169

Reviewed at https://rbcommons.com/s/twitter/r/421/

dturner-tw/pants,dgomez10/xanon,lahosken/pants,qma/pants,ericzundel/pants,baroquebobcat/pants,areitz/pants,di0spyr0s/pants,ericzundel/pants,pantsbuild/pants,gmalmquist/pants,jtrobec/pants,jessrosenfield/pants,laurentgo/pants,15Dkatz/pants,laurentgo/pants,foursquare/pants,laurentgo/pants,slyphon/pants,tdyas/pants,laurentgo/pants,mateor/pants,pombredanne/pants,pombredanne/pants,Gabriel439/pants,Gabriel439/pants,ity/pants,jessrosenfield/pants,TansyArron/pants,tdyas/pants,sameerparekh/pants,dgomez10/xanon,landism/pants,15Dkatz/pants,megaserg/pants,dgomez10/xanon,ericzundel/pants,UnrememberMe/pants,tdyas/pants,kslundberg/pants,kslundberg/pants,TansyArron/pants,pombredanne/pants,dturner-tw/pants,manasapte/pants,scode/pants,landism/pants,15Dkatz/pants,TansyArron/pants,lahosken/pants,jtrobec/pants,tejal29/pants,di0spyr0s/pants,twitter/pants,foursquare/pants,jsirois/pants,foursquare/pants,foursquare/pants,TansyArron/pants,kslundberg/pants,UnrememberMe/pants,pgroudas/pants,ity/pants,peiyuwang/pants,sid-kap/pants,di0spyr0s/pants,pgroudas/pants,gmalmquist/pants,pombredanne/pants,benjyw/pants,dturner-tw/pants,slyphon/pants,fkorotkov/pants,jessrosenfield/pants,benjyw/pants,twitter/pants,megaserg/pants,scode/pants,kslundberg/pants,jtrobec/pants,UnrememberMe/pants,laurentgo/pants,sameerparekh/pants,digwanderlust/pants,landism/pants,wisechengyi/pants,jessrosenfield/pants,lahosken/pants,wisechengyi/pants,wisechengyi/pants,twitter/pants,sid-kap/pants,peiyuwang/pants,wisechengyi/pants,cevaris/pants,jessrosenfield/pants,baroquebobcat/pants,sameerparekh/pants,pgroudas/pants,TansyArron/pants,kwlzn/pants,cevaris/pants,kwlzn/pants,ity/pants,dbentley/pants,manasapte/pants,Gabriel439/pants,cevaris/pants,lahosken/pants,areitz/pants,sid-kap/pants,digwanderlust/pants,dbentley/pants,sameerparekh/pants,landism/pants,baroquebobcat/pants,benjyw/pants,landism/pants,mateor/pants,dturner-tw/pants,benjyw/pants,wisechengyi/pants,twitter/pants,slyphon/pants,scode/pants,jtrobec/pants,ericzundel/pants,dturner-tw/pants,peiyuwang/pants,ity/pants,ericzundel/pants,laurentgo/pants,fkorotkov/pants,twitter/pants,dbentley/pants,gmalmquist/pants,ericzundel/pants,jtrobec/pants,jtrobec/pants,peiyuwang/pants,cevaris/pants,tdyas/pants,UnrememberMe/pants,digwanderlust/pants,jessrosenfield/pants,TansyArron/pants,pantsbuild/pants,ity/pants,15Dkatz/pants,Gabriel439/pants,wisechengyi/pants,manasapte/pants,mateor/pants,qma/pants,15Dkatz/pants,pantsbuild/pants,pombredanne/pants,sid-kap/pants,pombredanne/pants,dgomez10/xanon,15Dkatz/pants,square/pants,fkorotkov/pants,areitz/pants,pgroudas/pants,di0spyr0s/pants,foursquare/pants,tejal29/pants,peiyuwang/pants,dbentley/pants,pombredanne/pants,tdyas/pants,foursquare/pants,TansyArron/pants,landism/pants,scode/pants,fkorotkov/pants,scode/pants,megaserg/pants,slyphon/pants,foursquare/pants,cevaris/pants,tdyas/pants,jtrobec/pants,kwlzn/pants,foursquare/pants,wisechengyi/pants,UnrememberMe/pants,fkorotkov/pants,UnrememberMe/pants,tejal29/pants,peiyuwang/pants,dbentley/pants,kwlzn/pants,gmalmquist/pants,jsirois/pants,dturner-tw/pants,landism/pants,mateor/pants,qma/pants,scode/pants,jsirois/pants,di0spyr0s/pants,sameerparekh/pants,digwanderlust/pants,pgroudas/pants,mateor/pants,sid-kap/pants,mateor/pants,dgomez10/xanon,lahosken/pants,dgomez10/xanon,dgomez10/xanon,slyphon/pants,twitter/pants,gmalmquist/pants,kslundberg/pants,tdyas/pants,15Dkatz/pants,benjyw/pants,pgroudas/pants,dgomez10/xanon,twitter/pants,qma/pants,baroquebobcat/pants,kslundberg/pants,kslundberg/pants,megaserg/pants,areitz/pants,jessrosenfield/pants,kwlzn/pants,manasapte/pants,slyphon/pants,peiyuwang/pants,square/pants,digwanderlust/pants,twitter/pants,pantsbuild/pants,baroquebobcat/pants,areitz/pants,qma/pants,tdyas/pants,UnrememberMe/pants,kwlzn/pants,areitz/pants,ericzundel/pants,gmalmquist/pants,megaserg/pants,slyphon/pants,tejal29/pants,ericzundel/pants,lahosken/pants,fkorotkov/pants,manasapte/pants,wisechengyi/pants,sameerparekh/pants,dbentley/pants,qma/pants,sameerparekh/pants,cevaris/pants,di0spyr0s/pants,pantsbuild/pants,digwanderlust/pants,15Dkatz/pants,di0spyr0s/pants,lahosken/pants,pantsbuild/pants,scode/pants,fkorotkov/pants,landism/pants,benjyw/pants,square/pants,manasapte/pants,peiyuwang/pants,kwlzn/pants,areitz/pants,dgomez10/xanon,ity/pants,Gabriel439/pants,sid-kap/pants,sid-kap/pants,mateor/pants,baroquebobcat/pants,twitter/pants,tejal29/pants,megaserg/pants,megaserg/pants,baroquebobcat/pants,Gabriel439/pants,qma/pants,dbentley/pants,baroquebobcat/pants,gmalmquist/pants,tdyas/pants,benjyw/pants,fkorotkov/pants,UnrememberMe/pants,foursquare/pants,mateor/pants,wisechengyi/pants,baroquebobcat/pants,square/pants,dturner-tw/pants,Gabriel439/pants,dgomez10/xanon,lahosken/pants,cevaris/pants,ity/pants,dgomez10/xanon,manasapte/pants,pantsbuild/pants,UnrememberMe/pants