Updated the Dutch translation and fixed a few source strings

The layer data format and rendering order options only apply to tile
layers, which is now more clear.
Removed MapWriter::setLayerDataFormat/layerDataFormat

Now it just uses the layer data format set on the map, which simplifies
things a little.
tranditional Chinese translation
tiled_zh_TW.ts, fixed line 1153, put Chinese characters inside XML tag,
mark translations as Done, remove "type="unfinished"
Merge pull request #736 from yehnan/master

Tranditional Chinese translation
Updated Russian translation
Small fix to Russian translation
Updated Spanish translation
Fixed a missing space in two translations
Update Czech translation
Merge pull request #739 from encukou/cs

Update Czech translation
German translation update
Edited in @bjorn's comments from #733 and removed translated keyboard shortcuts
Merge pull request #741 from wayfu/master

German translation update
Added appdata file

The appdata currently fails validation since the fedora validator
does not yet support multiple licenses for the metadata.

Fixes #596.