Added the ability for a plugin command to have an alias in the CLI.
Added the ability for a plugin command to have an alias in the CLI.

This will be used by future plugins.

Review: https://reviews.apache.org/r/60087/

verizonlabs/mesos,reneploetz/mesos,dforsyth/mesos,asamerh4/mesos,asamerh4/mesos,gsantovena/mesos,Gilbert88/mesos,reneploetz/mesos,jpeach/mesos,verizonlabs/mesos,gsantovena/mesos,andschwa/mesos,andschwa/mesos,zmalik/mesos,dforsyth/mesos,andschwa/mesos,jpeach/mesos,dforsyth/mesos,asamerh4/mesos,gsantovena/mesos,chhsia0/mesos,chhsia0/mesos,Gilbert88/mesos,jpeach/mesos,kaysoky/mesos,abudnik/mesos,asamerh4/mesos,verizonlabs/mesos,zmalik/mesos,zmalik/mesos,gsantovena/mesos,Gilbert88/mesos,chhsia0/mesos,andschwa/mesos,zmalik/mesos,reneploetz/mesos,chhsia0/mesos,Gilbert88/mesos,kaysoky/mesos,verizonlabs/mesos,gsantovena/mesos,abudnik/mesos,jpeach/mesos,dforsyth/mesos,verizonlabs/mesos,andschwa/mesos,Gilbert88/mesos,dforsyth/mesos,jpeach/mesos,Gilbert88/mesos,asamerh4/mesos,reneploetz/mesos,gsantovena/mesos,andschwa/mesos,jpeach/mesos,chhsia0/mesos,kaysoky/mesos,abudnik/mesos,kaysoky/mesos,zmalik/mesos,abudnik/mesos,kaysoky/mesos,kaysoky/mesos,andschwa/mesos,asamerh4/mesos,dforsyth/mesos,verizonlabs/mesos,abudnik/mesos,zmalik/mesos,reneploetz/mesos,asamerh4/mesos,abudnik/mesos,reneploetz/mesos,zmalik/mesos,jpeach/mesos,dforsyth/mesos,abudnik/mesos,Gilbert88/mesos,reneploetz/mesos,kaysoky/mesos,chhsia0/mesos,verizonlabs/mesos,chhsia0/mesos,gsantovena/mesos