GroupClassGenerator: generate 1.6 bytecode!

It was still 1.5... There were two places to modify, not just one.
build.gradle: update Spring's propdep plugin dependency to 0.0.6
New RuleAnnotation enum

This enum associates annotations to rule methods with their descriptors.
RuleMethod: one small code change
RuleMethod: reformat
RuleAnnotation: add method to move flags from one RuleMethod to another
RuleMethod: move one usage of a boolean flag to the enumset instead
RuleMethod: remove one more boolean flag
RuleMethod: one more boolean flag removed
Fix one annotation visit bug...

We should not remove the whole check block. Not yet.
One more boolean removal in RuleMethod

Getting there, slowly!
RuleMethod: one more boolean flag removed (suppressNode)
RuleMethod: one more flag removed (suppressSubNodes)
RuleMethod: remove one more boolean flag (skipNode)
RuleMethod: one more flag removed

Only one left!
RuleMethod: remove all Types.* for annotations
Types: reformat, remove unnecessary modifiers, deprecate unused
Rename RuleAnnotation to ParserAnnotation
ParserAnnotation: rename recordDesc() to recordAnnotation()
ParserAnnotation: add BUILD_PARSE_TREE