Translate the tile list

Until now, the list of tiles in the layoutedit tab showed as title of a tile: the title minus ' Tile'. So: 'Basic Tile' becomes 'Basic'. That works, but makes the resulting string untranslatable.

In this pull request I add a `short_name` attribute to all tiles. In the base persistent tile this is empty. For any tile that inherits from the base tile and does not override this attribute, we fall back to the tile type title, with ' Tile' still appended.

This pull request also updates the manual.pot file, adding a few missing msgids and removing a few from tiles that are no longer available.