Update cs.xml

Translated string "Interface language"
Merge pull request #126 from Trottel/patch-2

Update cs.xml
constants
Merge branch 'master' into ice-cream-sandwich
Book UID (in progress)
Merge branch 'master' into ice-cream-sandwich
Merge branch 'master' of github.com:geometer/FBReaderJ
small updates in Norwegian translation
Merge branch 'master' into ice-cream-sandwich