cmake: Fixes and cleanup for libusb detection and version checks

The version checks are now enforced. (Fixes #130)

FindLibUsb now warns if the user is using < libusb-1.0.16, as this or
1.0.17 are *highly* recommended.

The redundant version check in Windows (ver.c) has been removed. Testing
with CMake 2.8.11.2 has shown check_library_exists() to be sufficient.
Update CMakeLists.txt
libbladeRF: Sped up flash writes, addressed log_info/debug consistency

Every flash page_write was being verified. Since we perform a readback
and verify, this is redundant and wastes time. This has been #ifdef'd
out (as it may come in handy for paranoid development checks from time
to time).

Some inconsistencies in log levels has been cleaned up.
libbladeRF: Support build with libusb-1.0.9

Although its use is not recommended (as later versions introduced USB
3.0-related fixes), the only thing holding back the build of
libusb-1.0.9 was a version check for debug purposes.

If libusb doesn't provide libusb_get_version() (1.0.10+), a dummy
function fills in a dummy string to denote this.
libbladeRF: Added debug/verbose log messages

These are intended to allow users to potentially glean a bit more info
in situations where the device is detected by the OS, but not by the
bladeRF library (and/or utils).
cmake: FX3 firmware build is disabled by default
libbladeRF: Continue probing for devices upon encountering failures

In cases where backends are unable to open a device, this allows another
backend to pick up the device. Specifically, there are a few controllers
that don't play nicely with libusb, but appear to work with the Cypress
driver/API.
libbladeRF: Print libusb error name on peripheral access failure
Update HDL and improve UART speed.

This updates the HDL and improves the UART speed significantly.
Rebuild application every time.
Added simulation model and compile script.
Fixed transmit timing out.
Fixed up reception and transmission.
Add signal mux.

Now muxing between internal signal generator and LMS6002D receiver.
Fixed up wrong default value for LMS.
Bump the firmware revision.
Bump version and remove FPGA fixup.
Selectively enable RF module.
More tweaks.  Still times out.
Reset.