Added support for suffixes on numeric values

Added a new conversion function that accepts a list of suffix to
multiplier mappings, and applies the appropriate multiplier to the input
value. Utilized this new conversion function in the CLI for set
bandwidth, set samplerate, and set frequency.
libbladeRF: Disable RF front end modules.

Instead of toggling all of power for all the RF modules when we
disable, just turn off the RF front end circuitry.  This alleviates
issue #82 since the PLL is powered separately from the RF front end.

Tested and verified that while TX was disabled, setting a new
frequency does have the spectrum show up at the appropriate place.
Merge branch 'issue66' of https://github.com/frank8371/bladeRF into frank8371-issue66

Enhancement to support suffixes on the command line.