Localisation changes in evolution/plugins

[Kjartan Maraas <kmaraas broadpark no>]

Hi.

I added the plugin descriptions for the caldav plugin and the
import-ics-attachment plugin to POTFILES.in and marked some strings for
translation in the eplug xml file so there's a couple new strings in
there to translate on the gnome-2-16 branch now.

Cheers
Kjartan