Translation updates for Koha 3.14.11 release

Added new language Khmer.
Update release notes for 3.14.11 release

Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
Merge remote-tracking branch 'translator/3.14.11-translate' into 3.14.x

Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
Increment version for 3.14.11 release

Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>