Add support for radio buttons in repeatable content.

This is done by uniquifying groups of radiobutton names using Behavior rules,
then converting back to original names before form submission in buildFormTree.
Added some unit tests for f:repeatable, covering basic usage, minimum parameter,
simple radio buttons and f:radioBlock.
Fixed handling of minimum parameter in f:repeatable, since the new test failed :-)


git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@29065 71c3de6d-444a-0410-be80-ed276b4c234a