bladeRF-cli: [WIP] First cut at RX DC auto calibration

Includes a workaround for convergence issues - further investigation
required. General cleanup and documentation changes still required.
bladeRF-cli: [WIP] Use fewer buffers for dc cal, start with cal at 0,0
bladeRF-cli: [WIP] Added TX DC cal operation. Further cleanup required.
bladeRF-cli: Check for divide-by-zero in interpolation function
libbladeRF: Be explicit with RXVGA2 cal.

It was seen that the VCM will sometimes come back in a bad state.
This register has a very well known value that it should be.  Setting
it to be these explicit values seems to help alleviate putting the
LMS is a bad state.

Investigation is required to figure out why the VCM is coming back
scrogged.
cli: Extend out DC, GAIN and PHASE max/min.