Add source compatibility 1.6

[leotilli]

Could you add source compatibility 1.6 when building Java libraries? Later on they could be referenced in projects that use JDK 6 to compile.

Currently, the generated jars include .class files with header 'cafe babe 0000 0033 ...' instead of 'cafe babe 0000 0032 ...'

[marcote]

Will be added in 0.10.2 on our Thursday release.