[BISERVER-10702] Flush session entries from cache when the session is logged out.

- Added call to logout a PentahoSession when the underlying HttpSession has expired.
- Flushing caches when Pentaho System is going down.
[BISERVER-10703] Adding defensive code to frame loading script to continue on in the event of an XSS exception.
Merge pull request #1078 from pentaho-nbaker/master

[BISERVER-10702] Flush session entries from cache when the session is lo...