Speed up switching between drive modes

[ryanlarkin]

Currently, there is a lot of reconfiguration that goes on when switching between drive modes. This can result in delays to switch modes.

See drivetrain-config

• [X] Use PID slots instead of sending new PID values
• [X] Try to reconfigure sensors as little as possible
• [X] Use different Talons for different sensor configurations
  • Front left/right for individual control
  • Back left combined drive forward
  • Back right combined rotation
• [x] Use SlotConfiguration class to configure slots rather than setting speed manually