Bug 536165 (RHQ-544)

basically, instead of attacking the problem from a bug fixing perspective (reactive) we need to be more proactive in detecting issues around updating plugins.  something like a series of files that test all possible update permutations to the rhq-plugin.xml files, and then runs them through our test harness.  even if we fail a number of tests, at least we'll know what mods we can survive, and where we fall down.  so, the more exhaustive this harness is the better; even if we find we initially fail many small tests, having the knowledge of what we can and can't do should help us to better estimate the remaining work to make plugin metadata updates perfect (or whatever we deem as an acceptable level of working-ness).