store sessions in the cache by default all the time
Refactor out common error handling
Use error base to display accessible error message
Create hook for plug-ins
Fix tests
Document session_store in doc/CONFIGURATION.md
Merge pull request #1265 from opf/feature/cache_store_by_default

store sessions in the cache by default all the time
Fix broken Work Packages Table when ?layout=false

Certain features, such as display of grouping headlines, appear to be
broken with layout hidden.

This bug helped banish another Prototype usage (`Element#getHeight()`)
from the code base. Using chainable `angular.element` (jQLite/jQuery)
we can handle a missing top-menu gracefully.

Bug # 9172

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Styled share modal buttons #8454
Merge pull request #1427 from opf/feature/4222_no_flash_message_on_status_page

[Fix] 7700 no flash message on status page
Update CHANGELOG.md
Merge pull request #1436 from opf/feature/work-packages-table-layout-false-fix

Fix broken Work Packages Table when ?layout=false