CamelKolabIMAPXProvider: build fixes
CamelKolabIMAPXProvider: build fixes

* include the single Camel lib header (via our
  Camel system header wrapper) instead of individual
  Camel headers (the latter is not allowed any longer)
* replaced CamelException with GError
* replaced CamelType with GType

GNOME/evolution-kolab,GNOME/evolution-kolab