ROO-3335: Roo creates new C.U. when entity changes

Merged contribution from Chema to retain JavaDoc and other comments.
ROO-3335: Roo creates new C.U. when entity changes

Upgraded antlr-java-parser to 1.0.7 for better comment support.
ROO-3335: Roo creates new C.U. when entity changes

Modified metadata structure to allow existing comments to persist through
modifications.  Also updated with changes from classpath-javaparser-fork
Merge pull request #26 from mikedehaan/ROO-3335-roo-creates-new-cu

Roo 3335 roo creates new cu