Make .ui file names match .c filenames
This only leaves the remaining inconsistently named .ui files:
- datetime: pages for differing date endianess, would need to be refactored if appropriate.
- mouse: Solved in !283
- network: Not attempted as @feaneron is planning to refactor.
- printers: Not attempted due to having momentum solving other structural issues.
- wacom: Needs some refactoring as .ui files are loaded in multiple places.