Plan status view

- bundle install
- rake db:migrate
Creates a view summarising the status of a plan (when sections were
locked and by whom, when questions were answered and by whom). Uses the
Schema Plusgem to generate the views (two supporting views needed) via
migrations. The idea is to improve the performance of the plan editing
page by reducing server load.
Also includes the Better Errors gem.
Streamlining

Trying to reduce system resources needed to view plan status
Better checking for unsaved answers

Use of isDirty() to check if TinyMCE text areas have been updated
without being saved is more reliable.
Checking for unsaved answers no longer requires an AJAX call.
Alert on closing section shows which answers are unsaved.
New alert on navigating away includes details of unsaved answers (could
be ordered better).
Needs further testing with other (non-textarea) question types.
Rolled back plan summary database view - was having a detrimental
effect on performance. Removed corresponding gem.
Visual tweaks

Avoiding long list of questions in unload alert; making “unsaved
answers” label more visible. Also fix for read-only access bug.
Refactoring plan editing JavaScript

Moved functions out of $(document).ready(), removed some duplication
Merge branch 'master' into Warn-when-navigating-away-from-plan

Conflicts:
	app/assets/javascripts/plans.js
	db/schema.rb
Merge branch 'Warn-when-navigating-away-from-plan'