libbladeRF: API change for get/set data transfer timeout

Addresses issue #202.

Fixed name and made return value an operation status rather than
returned value for consistency. We may need to make some
backend-specific calls here in the future, hence this interface
returning status.

The current implementation is not backend-specific, and has been moved
up to the top-level.
libbladeRF: Refactored correction functions and enumeration.
bladeRF-cli: Cleaned up correct command

Added return value and parameter checks. This command now ensures that the FPGA
is loaded. Performed misc. cleanup.
host: Fixed sample format misnomer - Q12 -> Q11

The sample format was incorrectly named, as there are only 11 fraction
bits, not 12.

The enumeration value has been renamed, and a macro definition is
provided for reverse compatibility. (This macro def will be removed
prior to the first "release.")
bladeRF-cli: Correct rx/tx error messages for invalid config params

Fixes issue #204