Update spell checker dictionaries

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Sync translations with Transifex

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Prepare release and bump version numbers to 1.8.10.0

Signed-off-by: Sven Strickroth <email@cs-ware.de>