[rilmodem] Implementation for call forwarding deactivation

User can try deactivate the call forwarding from keyboard instead
of erasure. Implementing lacking message

Signed-off-by: Jussi Kangas <jussi.kangas@oss.tieto.com>
Merge branch 'working-copy2'
Merge branch 'master' of github.com:nemomobile-packages/ofono
Merge branch 'master' of github.com:nemomobile-packages/ofono

Conflicts:
	ofono/drivers/rilmodem/call-forwarding.c
build: Added mnclenght plugin and driver
[ofono] Add MNC plugin changes from Canonical

Signed-off-by: Miia Leinonen <miia.leinonen@oss.tieto.com>
src: Auxiliar functions for MNC length plugins
include: MNC length from IMSI driver interface
plugins: Plugin for finding MNC length from IMSI

This plugin finds the MNC length from the IMSI using the valid MCC/MNC
pairs published by the ITU-T.
Merging Canonical MNC plugin changes

Conflicts:
	ofono/Makefile.am