Merge pull request #228 from jpoutiai/master

Refactoring rilmodem gprs implementation
[test] Add test script for explicit call transfer
[rilmodem] Explicit call transfer driver implementation
Merge pull request #229 from mkuukkane/transfer

Explicit call transfer rilmodem implementation
[voicecall] Cancel pending DTMF tones before hanging up call.
Merge pull request #230 from martinjones/master

[voicecall] Cancel pending DTMF tones before hanging up call.