Multidrive remote + touch interface fix

[2bndy5]

• fixes to touch interface touch interactions aren't working on the remote page sliders #78 , but needs math tweaking during webpage scrolling slider input innaccurate when remote page has been scrolled down #79 .
• added ability to select a drivetrain from remote.html using a dictionary of drivetrain objects.
• Roboclaw motor controller code is dirty hacked in for now; should migrate that over to Drivetrain repo.

Notes

To properly implement different controls for different drivetrains, We need to add the ability to customize the remote.html page based on drivetrain type or user settings #25