Update dutch.txt, also fixes #287 for Dutch

Also contains a few additional strings and fixes typos.
Added new OpenRCT2 strings for language switching
Extra translated strings, some fixed typos
Merge branch 'master' of https://github.com/Gymnasiast/OpenRCT2 into Gymnasiast-master

Conflicts:
	data/language/dutch.txt
Merge branch 'Gymnasiast-master'
Merge branch 'master' of https://github.com/IntelOrca/OpenRCT2

Conflicts:
	data/language/dutch.txt