Allow session offerings to be counted only once

Sessions like small groups may have many offerings, but each student
only attends a single time.  This allows users to mark these sessions
specially so they can be counted correctly in reporting.
Shorten language title for spacing
Use count offerings once in report
Count offering duration in hours not minutes
Cleanup CI session/course model
Display session hours dynamically

When a user selects/deselects count offerings once in the sessions
table we update the total time column accordingly.
Add user instructions to session summary
Add a link to view session details in the summary
Fix div id remove dead code
Add check/uncheck all to session block count

Users can no select count as one for all/none of the sessions.  Also
used this to default new session block courses to being completely
selected.
Make the count offerings description smaller
Add filtering to sequence block table