Ref #227, Display content access statistics.

This commit brings a way to show the access statistics in the interface for items: event viewing, event content download stats, grade book views, document sharing views/downloads. It also cleans up the history_log() done in the learning events section, with an entry now created when the event is created, either through add, copy, or draft. In the past the changes weren't logged until a second person worked on the event.
Brings feature-statistics in line with develop.
Adds statistic model, moves in page queries into statistics model. Updates markup to put tabular data into tables and implements datatables for client-side column sorting. Moves modal calls to bootstrap and jqueryui from prototype, where appropriate. Updates API files to return json / removes api files that are handled in page.
Merge pull request #448 from EntradaProject/feature-statistics

Ref #227, Display content access statistics.