bladeRF: handle USB serial number string requests
fx3_firmware: bump firmware version to 1.2
libbladeRF: fix libusb string descriptor fetch

This commit fixes libusb_probe()'s return value when
libusb_get_string_descriptor_ascii() returns successfully.
bladeRF-cli: Added simple non-tecla based interactive mode support

This will allow folks without libtecla installed to use a simple (albeit
less feature-rich) interactive mode and script support. Interactive mode
is now always compiled in, and the build option, ENABLE_INTERACTIVE_TECLA
has been replaced by ENABLE_LIBTECLA.

The simple fgets-based implementation currently does not support path expansion.
host: Disabled file and line information from log messages by default.

This information (which is helpful when asking questions on IRC or
in the forums), can be enabled via the CMake argument,
     -DENABLE_LOG_FILE_INFO=ON
libbladeRF: Failure to read serial # made non-fatal.

If we fail to fetch the serial number due to older firmware, this
would prevent the user from being able to get far enough to upgrade.
Therefore, we instead opt to print an error message and trudge onward.
hdl: Updated README.md to suggest reconfiguring dash rather than manual symlinking
libbladeRF & bladeRF-cli: Fixed potentially uninitialized variables

If a flash calibration or OTP section are either corrupted or not set
the serial, trim, and FPGA size will not be read back. Under these
conditions, some "dummy" values are populated in the device structure,
to avoid uninitialized variables being thrown around.
libbladeRF: Added 200 ms delay in FPGA poll loop, yielding a 2s timeout
libbladeRF-test: Stubbed out a repeater test/example
test_repeater: Added additional init