BISERVER-9592 - Changing the theme causes users to lose unsaved content.

What was done:
1) added corresponding changes to resource files
2) changed SwitchThemeAction

BISERVER-9592 - Changing the theme causes users to lose unsaved content.

What was done:
1) fixed a typo in the message
Merge pull request #1375 from kolinus/BISERVER-9592

BISERVER-9592 - Changing the theme causes users to lose unsaved content.