Huge update to the TDG branch, bringing it all the way up-to-date with the main GSMSHIELD branch

This pull request includes:
- reformatting of everything, spacing/line-endings
- includes changes from @MarchMartines to move strings to flash memory, save RAM
- fixes to httpGet() and httpPost()
- fix to setting GSM_ON and GSM_RESET to output before writing to them