Re-make Ganglion ECG Tutorial

[retiutut]

https://docs.openbci.com/GettingStarted/Biosensing-Setups/ECGSetup/#3-lead-ecg-with-cyton-or-ganglion-boards

This part of the tutorial was not able to be replicated with success. It contains an incorrect picture of a Cyton and other extraneous information. This entire section should be redone.

[retiutut]

Thanks to the recent Ganglion firmware update from @philippitts, this ticket is now possible!

Re-attempt this ticket using Ganglion firmware v3+. https://github.com/OpenBCI/OpenBCI_Ganglion_Library/releases