Fix for #77.  Cleaned up data w.r.t. to devices having serial numbers wi...

...th trailing whitespace.

Notes:
- ref de3040aa, which is a fix made ages ago to make sure that all textfield input is trimmed of whitespace before making it to the database.  Unfortunately, that fix didn't include cleaning up the existing non-trimmed data.
- the results of this migration can be verified by ensuring that the following sql returns '0': ```select count(*) from aatams.device where serial_number like '% ';```
- @julian1 has made a backup of the production DB on the afternoon of 30/04/2014.