Set description in Picasa export only if it is defined

Otherwise Picasa displays filenames as photo descriptions, which is not nice in exported albums
Use Google's terminology in variable names - title/summary, instead of caption/description

Title is the filename and summary is something that is displayed along with the photo on the web (xmp title).
Danish translation: Better translation for lossy/lossless
Merge remote-tracking branch 'upstream/master'
Danish translation: Better translations of some strings
Fix #9665: Allow toggling filmstrip in map view

Maybe we should move that code to lib/tools/filmstrip.c?
Merge pull request #315 from angryziber/master

Improve Picasa export: do not set irrelevant summary for photos consisting of a filename, keep it empty if xmp title is not defined instead
allow longer string length for camera maker/model and lens name

affects cached image data and lens correction module. should fix #9644.
focus: clip focus regions to cropped image.
focus: slight performance fix.
focus: don't display stale old clusters
Fix some strings marked for translation

YEAH! Finally I found time to fix some bogus strings before string
freeze. :)
[l10n]: Update of German translation
Update French translation.
Merge remote-tracking branch 'upstream/master'
Updated Danish translation
Merge pull request #341 from pryds/master

Updated Danish translation
Italian translation updated
Merge pull request #342 from bartokk/master

Italian translation updated
collect: Improve tag mode a bit

- Allow translation of "uncategorized"
- Get rid of some GTK warnings
- Don't remove subtrees not matching, just collapse them so it's easy to
  click around