Update UK data for May 2014 boundaries and postcodes

This provides a control file and two management commands to fix up the
boundary data for the May 2014 edition of Boundary-Line.

No areas are manually altered in the control file, but some new geometries
introduced in this edition had to be manually fixed, and an error from the
previous 2013-10 edition had to be corrected.

The order that these management commands are run is important, and should be:
1. `./manage.py mapit_UK_fix_2013-10-south-tynedale`
2. `./manage.py mapit_UK_import_boundary_line`
3. `./manage.py mapit_UK_fix_2014-05`

Closes #119