Support for Hz, KHz, MHz, Ghz notation in the settings

[BSAsecure]

For less powerful users it is easier to introduce values like Bandwidth, Frequency, Sample Rate in the Hz, KHz, MHz, Ghz.

It could be achieved by simple drop down menu with Hz->GHz value or support for input values like "1.6MHz"

Support for GnuRadio like inputs "1e7" / "1e+7" is also useful.