[LUA API] new radio.* functions group

[JimB40]

Group radio functions in own 'class/object'

defaultChannel -> radio.getDefaultChannel() defaultStick -> radio.getDefaultStick() getAvailableMemory -> radio.getLuaAvailableMemory() getUsage() -> radio.getLuaUsage() getDateTime -> radio.getRtcDateTime() getRtcTime -> radio.getRtcTime() getTime - > radio.getTime() getFieldInfo -> radio.getFieldInfo() getGeneralSettings -> radio.getGeneralSettings() getGlobalTimer -> radio.getGlobalTimer() resetGlobalTimer -> radio.resetGlobalTimer() getRAS -> radio.getRAS() getRotEncSpeed -> radio.getRotEncSpeed() getTxGPS -> radio.getGPS() getVersion -> radio.getVersion() multiBuffer -> radio.MultiBuffer() serialRead -> radio.serialRead() serialWrite -> radio.serialWrite() setSerialBaudrate -> radio.setSerialBaudrate()

getFlightMode -> isn't duplicated with model.getFlightMode and should be depreciated???