(Minor) Incorrect packet name for core value requests

[brentyi]

https://github.com/mit-racecar/vesc/blob/master/vesc_driver/src/vesc_packet.cpp#L240

This bit:

VescPacketRequestValues::VescPacketRequestValues() :
  VescPacket("RequestFWVersion", 1, COMM_GET_VALUES)

Should probably be:

VescPacketRequestValues::VescPacketRequestValues() :
  VescPacket("RequestValues", 1, COMM_GET_VALUES)

There's currently no functional difference (from what I can see), but this could cause problems in the future.