Allow retrieving translations for multiple tiles in one call

[retep998]

Currently if I want to fetch a bunch of translations for a lot of tiles I have to do a request for each tile. I would prefer to be able to get the translations for multiple tiles in a single request. Possible options:

• Allow tsid to be optional. If this option is left out, retrieves translations for all tiles.
• Allow tsid to be a | separated list of tile ids, so tsid=1244|1245|1246 for example.
• Add tslimit parameter, as retrieving translations for all tiles at once may be too large of a result and there needs to be a way to control how many results are returned per request, with a way to continue of course.