Bugfix for GVARS in weight for stock and ranges for ARM based transmitter

For All:
- GV1_XXX constants are now in myeeprom.h to be close to the mixer defines
  (they need to match to the defined types, e.g. needs to have enough bits)

For Stock:
- bugfix gvars not working for weight for stock transmitter

For ARM based Transmitter:
- limits offset now to 490 (instead of 4085)
- limits for weight and offset can be easily changed in myeeprom.h, with defines
  #define GV_RANGE_WEIGHT 500
  #define GV_RANGE_OFFSET 490
  (be sure they are not bigger than something about 4000)

No code cost