userportal, webadmin: Added caching

- Refactored frontend into frontend jar and frontend overlay.
The overlay now contains the servlets, while the frontend
contains the logic.
- Refactored view code from servlet into JSP.
- Removed cache 'buster' parameter for nocache.js.
- Added CachingFilter to properly set caching based on regular
expression pattern matching.
- Updated servlet version to 3.0 for relevant servlets.
- Added unit tests for CachingFilter, PageServlets.
- Added code to calculate MD5 for relevant page information
so it can be used as the ETag for the home page.

Change-Id: I5d8e02ae542a4aa37bd421bde5582c0f3e9820ad
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=875814
Signed-off-by: Alexander Wels <awels@redhat.com>