Adding new ARX control scripts

New ARX control script, to replace AspController scripts. Allows the reading and writing of ARX calibration files, and easier control of all four ARX shelves @ LEDA-OVRO. Also added auto tuning and setting of ADC gains.

Housekeeping: moving valon -> control/valon_control
Signed-off-by: Danny Price <dan@thetelegraphic.com>