Move documentation files to /doc
Add gerber files for the panelized version

The gerber folder contains all the necessary files for PCB production.
 - *.gb? *.gt? are standard Gerber files (RS-274x) for the several PCB
   layers;
 - *.drl are KiCad generated drill files (Excellon format)
 - *.txt is a 'merge' of previous drl files to fit Seeedstudio upload
   requirements (Using MergeDrl.pl, see cjlano/kicad-utils)
Those files were sent to Seeedstudio for successful manufacturing.