libbladeRF: Load calibration tables or FPGA bitstream on device open

On Linux and OSX, the following directories will be searched,
in the order listed:
    ~/.config/Nuand/bladeRF
    ~/.Nuand/bladeRF
    /etc/Nuand/bladeRF

In Windows, %appdata%/Nuand/bladeRF will searched.

The following files will be loaded, if found in these search paths:

    FPGA image: hostedx40.rbf or hostedx115.rbf, depending on the
                size of the FPGA reported by the device.

    DC Calibration tables: <serial>_dc_<rx|tx>.tbl