bladeRF-cli: Added log level verbosity as a cmd line switch

The -v or --verbosity flag can be used to set the libbladeRF verbosity.
In the future, we should also start using this to potentially supress
CLI output.

Also fixed in this commit:
    - bladerf_open() typo in help text
    - Removed "b" option from OPTSTR, as this is no longer supported