libbladeRF: Refactored lms code, implemented baseband and RF loopback

Changes include stylistic and functional clean-up. LMS functions now
return and check status codes.

Finer grained loopback options have been added.
libbladeRF: Bumped version to v0.13.0

Changes include:
    - LMS refactoring and loopback support
    - Support for passing NULL to optional API parameters
    - Dummy backend
    - Bug fixes
bladeRF-cli: Added loopback support to 'print' and 'set' commands
bladeRF-cli: Added gain VGA gain ranges to help text
bladeRF-cli: Bumped version to v0.10.4

Changes include:
    - Loopback support added to print/set commands
    - Bug fixes