gril: Add functions for reading a string array
gril: Separate parsing of registration replies

Previously, replies to RIL_REQUEST_VOICE_REGISTRATION_STATE and
RIL_REQUEST_DATA_REGISTRATION_STATE were parsed using the same
function. This change separates the parsing of these replies, as the
data that is different for each type could be eventually needed.
Additionally, state parsing has changed so now all RIL states are
mapped to valid ofono core status values and the right max_cids is
returned for MTK modems.
rilmodem: Adapt drivers to change in reply parsing

gprs and network drivers are affected by the change for separating
the parsing of the replies to data/voice registration state requests.
unit: Adapt to changes in reply parsing
Merge pull request #87 from alfonsosanchezbeato/regstate

Separate registration state parsing for voice and data