Added note about implicit default filter to javadoc.
Added note about implicit default filter to javadoc.

Makes framework developers aware that the MesosSchedulerDriver will
add an implicit filter declining unused resources.

Review: https://reviews.apache.org/r/43491/

dforsyth/mesos,jpeach/mesos,Aman-Jain-14/customizedMesos,craimbert/mesos,verizonlabs/mesos,dforsyth/mesos,Gilbert88/mesos,gsantovena/mesos,craimbert/mesos,jpeach/mesos,jpeach/mesos,reneploetz/mesos,Gilbert88/mesos,verizonlabs/mesos,chhsia0/mesos,zmalik/mesos,chhsia0/mesos,yuquanshan/customizedMesos,craimbert/mesos,Gilbert88/mesos,neilconway/mesos,kaysoky/mesos,yuquanshan/customizedMesos,asamerh4/mesos,Gilbert88/mesos,jpeach/mesos,zmalik/mesos,jpeach/mesos,reneploetz/mesos,asamerh4/mesos,kaysoky/mesos,craimbert/mesos,craimbert/mesos,reneploetz/mesos,zmalik/mesos,reneploetz/mesos,Aman-Jain-14/customizedMesos,abudnik/mesos,asamerh4/mesos,andschwa/mesos,Gilbert88/mesos,reneploetz/mesos,chhsia0/mesos,neilconway/mesos,jpeach/mesos,chhsia0/mesos,yuquanshan/customizedMesos,verizonlabs/mesos,kaysoky/mesos,chhsia0/mesos,dforsyth/mesos,chhsia0/mesos,abudnik/mesos,Gilbert88/mesos,gsantovena/mesos,chhsia0/mesos,asamerh4/mesos,gsantovena/mesos,zmalik/mesos,jpeach/mesos,yuquanshan/customizedMesos,verizonlabs/mesos,zmalik/mesos,kaysoky/mesos,andschwa/mesos,andschwa/mesos,Aman-Jain-14/customizedMesos,gsantovena/mesos,abudnik/mesos,andschwa/mesos,Aman-Jain-14/customizedMesos,dforsyth/mesos,abudnik/mesos,yuquanshan/customizedMesos,verizonlabs/mesos,dforsyth/mesos,yuquanshan/customizedMesos,andschwa/mesos,neilconway/mesos,neilconway/mesos,andschwa/mesos,kaysoky/mesos,dforsyth/mesos,Aman-Jain-14/customizedMesos,abudnik/mesos,dforsyth/mesos,gsantovena/mesos,neilconway/mesos,andschwa/mesos,neilconway/mesos,verizonlabs/mesos,craimbert/mesos,reneploetz/mesos,Aman-Jain-14/customizedMesos,gsantovena/mesos,zmalik/mesos,asamerh4/mesos,asamerh4/mesos,yuquanshan/customizedMesos,verizonlabs/mesos,kaysoky/mesos,kaysoky/mesos,zmalik/mesos,Aman-Jain-14/customizedMesos,craimbert/mesos,gsantovena/mesos,abudnik/mesos,reneploetz/mesos,asamerh4/mesos,neilconway/mesos,Gilbert88/mesos,abudnik/mesos