Recreate pot and po files

Although we have already string freeze, we need to recreate the
translation files again.

* These changes remove the 'Ok', instead we will only have 'OK'
  One way of spelling removes the burden of translations.

* We introduced 'Trade' as engine string. This is most often already
  translated, so it was just uncommented most of the time.
translation-de: shorten mouse button names.
Enable exit menu when transformed
Allow Character menu to be open when transformed
xgettext is utf8 safe now
Translations: Bump version number to 0.18
Merge remote-tracking branch 'mainline/master'

Conflicts:
	mods/default/languages/engine.pl.po
	mods/default/languages/xgettext.py
Update version number in pot and po files.
Updated Japanese translation for engine.ja.po.
Looks a bit weird seeing "Nihongo", "Japanese" is far more appropriate. "日本語" would be even better, but loading a larger font just for that seems a little bit of a waste.
Merge remote-tracking branch 'upstream/master' into bugfixes
Merge pull request #489 from Paul-Wortmann/master

Updated Japanese translation for engine.ja.po.
Merge pull request #486 from dorkster/bugfixes

Enable some menus when transformed
Fix flavor text for items in xgettext tool.

Fixes #492.
Merge remote-tracking branch 'mainline/master'

Conflicts:
	mods/default/languages/engine.ja.po
Allow specifying a range for item/currency loot
This obsoletes the hardcoded gold drops amounts by level for enemies.
Fix bonus_currency
Need sleep
Only show one tooltip context at a time

Closes #491

Tooltips can either be in the context of the map (events and NPCs), or
in the context of menus. Menu tooltips will always take priority over
map tooltips.
Allow map events to trigger music changes

Closes #494