* add a little Stash utility.
* add radio state RAII helper.
* first part of radio_state changes
* add radio_state_ to rest of apps
* fix freq_step and format
* fix unused ui_sigfrx: corrected sample rate, added back freq setting
* ui_transmitter : Added rf_amp field
* ui_transmitter : Added color grading depending on gain settings
* Removed TransmitterModel::set_rf_amp(bool) call from every apps loading ui_transmit
* transmitter_model : RF_amp disabled by default
* APRS Tx app : Fixed frequency keypad not showing up
* Morse Tx app : Removed TransmitterModel::set_lna() and TransmitterModel::set_vga() calls