plugins: Add rildev for creation of ril modems

This new plugin will create ril modems, providing the same
functionality as udev/udevng does for USB-based modems.
build: Add rildev plugin
gril: Close properly socket
test: add exception handling to some scripts

Add exception handling to 'enable-modem' and 'list-modems',
so that they don't crash when ofono isn't running and/or
hasn't completely initialized.
rilmodem: add call-forwarding atom

Add call-forwarding atom from nemobile github repository:

https://github.com/nemomobile-packages/ofono/tree/master/ofono

The original authors of this code are:

Jussi Kangas <jussi.kangas@tieto.com>
Jarko Poutiainen <Jarko.Poutiainen@oss.tieto.com>
gril: add call-forwarding support

Add parcel building/parsing functions for call-forwarding support.
rilmodem: clean/re-factor call-forward atom

Clean up the call-forward atom by reducing code
duplication, and re-factoring to use new grilreply/
grilrequest parcel functions.
build: enable rilmodem call-forwarding atom
plugins/ril: enable call-forwarding support
Merge pull request #58 from tonyespy/test-script-exceptions

Tested on mako
test: add argument parsing to test-call-forwarding
Merge pull request #55 from tonyespy/call-forwarding

Call forwarding
Merge pull request #54 from alfonsosanchezbeato/vendor-select

Dynamic loading of ril-type modems
gril: Add parcels for radio-settings driver
rilmodem: Add radio-settings driver

This driver adds support for setting the preferred radio technology.
It provides ofono support to set the preferred cellular radio (see
https://bugs.launchpad.net/ubuntu-system-settings/+bug/1211804).

Based on nemomobile implementation:

https://github.com/nemomobile-packages/ofono/tree/master/ofono

The original author of this code is Jussi Kangas
<jussi.kangas@tieto.com>.
build: Compile ril radio-settings module
ril: Create radio-settings interface
unit: Add tests for ril radio-settings parcels
Merge pull request #53 from alfonsosanchezbeato/radio-settings

Radio settings
test: Switch scripts to run with Python 3