[WFCORE-259] Update realm readiness checking to be based on having at least one mechanism ready for challenge/response style authentication.
[WFCORE-213] :  Clean unreferenced items from the content repository

Now we are using ContentReference to track contents in the content repository.
Now we are tracking references to overlays.
Trying to use server group definition for domain mode.
Simplifying ContentReference
WFCORE-211: Fixing overzealous cleaning of HC content.
[WFCORE-178] :  ContentRepositoryImpl should not call File.deleteOnExit when deleting content.

Using the new Path API instead of File.
Cleaning empty old directories.
[WFCORE-260] Minor corrections for use with the IBM JVM.
Merge pull request #284 from ehsavoie/WFCORE-213

[WFCORE-213] :  Clean unreferenced items from the content repository
[WFCORE-264] The validator also needs the flag setting to say it supports expressions.
[WFCORE-253] The validator also needs the flag setting to say it supports expressions.
Merge pull request #336 from darranl/WFCORE-259

[WFCORE-259] Update realm readiness checking based on ability to challenge.
Merge pull request #340 from darranl/WFCORE-260

[WFCORE-260] Minor corrections for use with the IBM JVM.
Merge pull request #344 from darranl/WFCORE-253

[WFCORE-253] / [WFCORE-264] Correct the String length validation to support expressions.