libbladeRF: Added simple full-duplex repeater test

This test program re-transmits received data in real time (optionally on
a different frequency.)
libbladeRF: si5338 refactored to support fractional sample rates.
libbladeRF: bladerf_load_fpga no longer checks current FPGA status

This check was only being used to print an informational message.
However, it was supposed to be used to change the return value to
indicate the FPGA being re-loaded versus loaded.

Because the caller can check the FPGA state via
bladerf_is_fpga_configured(), this check has been pulled out, and the
interface now specifies that this functions return value only indicates
success (0) or failure (error code).
libbladeRF: Cleaned up a few minor Doxygen warnings
libbladeRF: Clarified a few items in the header documentation.
[libbladeRF] Exposed erase/read/write functions
[bladeRF-cli] Added erase option to cli
[libbladeRF/bladeRF-cli] Added support booting directly from the FX3 bootloader
[libbladeRF bladeRF-cli] Change name of FX3 bootloader firmware load to recover
 Also changed CLI to take device string instead of bus and address
Added udev rule for FX3 bootloader
[libbladeRF] Refactored libusb search to use common methods
[libbladeRF] Added support for searching for FX3
[bladeRF-cli] Added message to indicate an open in the CLI is now required
[libbladeRF] Added check for FX3 bootloader in lusb_open and lusb_probe
 - This informs users that a FX3 bootloader was detected.  The user
   will need to determine if that device is a bladeRF FX3 or not
[libbladeRF] tab->space for ezusb.c
[libbladeRF] Fixed logging levels
Initial JUMP_TO_BOOTLOADER support
 - Added method to libbladeRF
 - Added new VID/PID pair to udev rule to prevent requiring root access
 - Added jump_to_boot bladeRF-cli command
 - Fixed most warnings in FX3 firmware
[bladeRF-flash] Initial version
Initial version of bladeRF-flash tool
Fixes found during testing of bladeRF-flash
 - Looks like trying to transfer data just before a RESET doesn't complete
   Changed RESET vender request to data-less
 - Fixed some missing new line chars