Removed stopwatch.php

- We've got some dead .php code, and stopwatch was a part of it.
  Once I've got some time I shall weed out the valueManager and the database parts.
- Since much of the formerly time intensive work is now performed client side,
  the stopwatch became unnecessary.
Fixed selection of RfcLanguages in translation interface

- Closes #34
- The selection now also displays the study that a RfcLanguage belongs in,
  to reduce confusion arising from duplicate RfcLanguage names like RP, 'German (DE)' or 'Rfc. Spelling'.