[BZ 1022943] Ability to trigger update of plugins on agents from UI and API
This is stage 1 of the series of commits to enable more user-friendly
handling of plugin updates.

It provides basic support for triggering updates of plugins on agents
by calling server-side APIs/GUI.
Merge remote-tracking branch 'origin/master' into bug/1022943

Conflicts:
	modules/enterprise/server/itests-2/src/test/java/org/rhq/enterprise/server/test/TestAgentClient.java
	modules/enterprise/server/jar/src/main/java/org/rhq/enterprise/server/agentclient/AgentClient.java
[BZ 1022943] Added ability to check status of plugin update on agents
Merge remote-tracking branch 'origin/master' into bug/1022943

This is to have the fix for BZ 1076389 (which blocks BZ 1022943) in this branch.
[BZ 1022943] Fixes to PluginCriteria
[BZ 1022943] Reporting changes of plugin deployments
note in the javadoc that the deploy* methods are synchronous.
[BZ 1022943] Added a new REST endpoint for working with agent plugins.
Merge master into bug/1022943 reflecting disappearance of plugin purge
[BZ 1022943] Fix delay selection dialog in UI.
[BZ 1022943] Remove remnants of plugin purge from criteria class and REST.
Merge remote-tracking branch 'origin/master' into bug/1022943
[BZ 1022943] Arguments sanity check in ContentHandlerBean#provideAsPlugin()
[BZ 1022943] Correct @PUT and @POST, improve response of register() method.
[BZ 1022943] Don't duplicate the test setup that can be shared.
Merge pull request #4 from metlos/bug/1022943

[BZ 1022943] Ability to trigger update of plugins on agents from UI and API