Add screenshots to Notifications / Action Triggers docs

[Remington Steed]

This bug will attempt to track progress on reviving the "Notifications / Action Triggers" section from the 2.0 documentation and reintegrating it with the master docs.

Working branch in progress:

user/rsteed/revive_old_action_triggers_docs

http://git.evergreen-ils.org/?p=working/Evergreen.git;a=shortlog;h=refs/heads/user/rsteed/revive_old_action_triggers_docs

Thanks to yboston's intern who converted this doc from DocBook into AsciiDoc.

[Remington Steed (rjs7)]

Force pushed a few small corrections, and picked the commit into master. The new section should appear in the live docs after the docs rebuild tonight.

[Remington Steed (rjs7)]

The published version of this doc can be found here:
http://docs.evergreen-ils.org/dev/_action_triggers.html

This doc still could use some screenshots, so I am reopening this bug and adding the bitesize tag.

[Remington Steed (rjs7)]

Note, my previously posted URL is broken. Action Triggers docs are now here:
http://docs.evergreen-ils.org/dev/_notifications_action_triggers.html

[Andrea Neiman (aneiman)]

PR'd here:

https://github.com/evergreen-library-system/Evergreen/pull/77

I also added language about Message Center-related Event Defs, and pulled in language from Remington's link in comment #3 about testing, since I didn't see that in the consolidated manual version of the a/t page.