Merge two cases for the same contact into a single case

Rationale
========
Two cases have been created for the same contact, either by mistake or because it was the correct decision at the time but new information now indicates they should be counted as the same case.

Implementation
============
1. Add 'Merge Case' link to Case Summary fieldset on Manage Case screen (contact/view/case) - IF there are other (not deleted) cases for this client.
2. Clicking link shows <select> dropdown + 'Merge' button. Dropdown has an option value for each other case belonging to this client. Option label s/b

'Case ID: ' + $caseID + 'Type: ' + $caseType + ' Start: ' + $caseStartDate

3. Merge processing does the following:

• Move source (currently viewed) case to trash
• Make copies of any non-singleton activities including prior revisions and associate them with the destination case.
• Auto-add an activity to the case with subject "Case #1234 merged into case #5678". The activity details field should contain a list of the date, activity type and subject line (if subject is present) of all the activities that were copied to the target case.
• Redirect user to Manage Case screen of target (merged TO) case