Import rilmodem implementation from Ubuntu

Taken from http://bazaar.launchpad.net/~phablet-team/phablet-extras/ofono/ at revision 31
+ https://code.launchpad.net/~awe/phablet-extras/ofono-sim-support/+merge/158469 for SIM
support

Signed-off-by: Simon Busch <morphis@gravedo.de>
Add plugin for GPRS provisioning support through the Android APN database