Addressed comments from face-to-face with Peter and Kieran.

[mhhen]

• Issue #3: Adding user pointer to GccSglEntry and GccgSgList structures.
• Issue #4: Added GccgInitialize() and GccgEventLoopPoll() APIs.
• Issue #5: Added TMin/T99 accumlated SON elements and new returned JSON structure to support them and returning Workstep's TMin/T99.
• Issue #6: Added comments to GccgTxCallback() and GccgRxCallback() APIs about thread usage.
• Issue #7: Changing to use firstField instead of evenField and updated comments.