Add event handles to param pool

As per #2149
Merge remote-tracking branch 'origin/integration' into events
Make handle of value
Fix Author field output on entry tables. Fixes #2172
Merge pull request #2170 from embarknow/events

Make page's events accessible in the param pool. Closes #2149
Clear filter results after each Event delegate to prevent duplicate nodes in the Event XML. Closes #2179
Merge branch 'integration' of github.com:symphonycms/symphony-2 into integration