Merge pull request #44 from ministryofjustice/safe-renames-78206202

Rename some prisons
fixing isle of wight's visiting times and numbers
Merge pull request #45 from ministryofjustice/fix_iow_times

fixing isle of wight's visiting times and numbers
Fix specs for recent content & data changes
Simplify unbookable spec
Merge pull request #46 from ministryofjustice/fix_specs

Fix specs for recent content & data changes
Added an auxiliary field to the Prisoner model.
VisitController saves the prison data structure for future use.
VisitHelper doesn't refer to any globals anymore. Fixes to templates, and tests that are related to that.
Normalized some test data.
Added a conditional in the controller to work around issues with tests.
Removed legacy data handlers which are no longer needed.
Migrate old session data.