Add "Room Language is… en/de/nl/…" as a per room setting

[akempgen]

add a per room setting "room language", so colloquy knows what language is spoken by the members of a chan, because it looks weird to have german join/part messages in an english transcript and vice versa…

this could affect room event messages, script output (itunes, slap messages, wikipedia (see #760), etc) and probably other stuff too. for this to work, the setting should be available to plugins, of course.

[timothy]

Neat idea!