[BZ 1069547] Support shutdown of domain controller in ServerControl

This fixes the patching domain controllers which failed if restart
was demanded during the deployment.

Also optimized the reading of host.xml (to find the host of the domain
controller in the domain) to use SAX parser instead of DOM. This is
much lighter on resources and should also be much quicker because we
only need to read first couple of lines of the file.
[1001383] getResourceConfiguration does not return the current resource configuration
Improve some ConfigurationManagerRemote javadoc, making it more clear that
getLatestResourceConfigurationUpdate() satisifies the API request in the BZ (I think).
BZ 1124619 - provide more responsiveness when you want to ask an agent to update itself from the GUI. There is now a "update agent" operation, rather than requiring the user to use "update --update".
[1001383] getResourceConfiguration does not return the current resource configuration
Further improve the confusing/incomplete javadoc surrounding the get/find
configuration remote API methods.
BZ 1088032 - show a warning message if readlink doesn't exist.
[BZ 1070299] Added auto-start description from the EAP 6 documentation. The functionality for auto-strart field was already correct, just adding field description to avoid confusion.