Updated danish translation by Thomas Pryds.
drawn masks : disable colorpicker
mask manager : fix a pb to unselect active group
Fix: 18 fuzzy translations, 17 untranslated messages.
Merge branch 'master' of https://github.com/darktable-org/darktable
pl.po - fix 8 fuzzy, 8 untranslated messages
Fix: 4 fuzzy translations.
Merge pull request #236 from adsr303/plpo

pl.po - fix 8 fuzzy, 8 untranslated messages
Button to select between to split view or overlay
Create snapshots table and add a snapshot number column to images table
Several snapshots history and name saving

 + Write snapshot's history to xmp (TO BE FIXED)
 + Write snapshot's history to db
 + Write snapshot's name to db
TODO: we also need to read snapshots info from xmp file
Small modification in colums name in snapshots table
Make sure the functions are defined before using them
Create snapshots table and update history one in existing db
Read all the snapshots information from the db and store it in the sidecar
Fix several compile errors
Read snapshots' history from XMP sidecar files