add source for rf103 (experimental)

owrx/feature.py

@@ -68,6 +68,7 @@ class FeatureDetector(object):
         "red_pitaya": ["soapy_connector", "soapy_red_pitaya"],
         "radioberry": ["soapy_connector", "soapy_radioberry"],
         "fcdpp": ["soapy_connector", "soapy_fcdpp"],
+        "rf103": ["rf103_sdr"],
         # optional features and their requirements
         "digital_voice_digiham": ["digiham", "sox"],
         "digital_voice_dsd": ["dsd", "sox", "digiham"],
@@ -492,3 +493,6 @@ class FeatureDetector(object):
         [OpenWebRX wiki](https://github.com/jketterl/openwebrx/wiki/DRM-demodulator-notes).
         """
         return self.command_is_runnable("dream --help", 0)
+
+    def has_rf103_sdr(self):
+        return self.command_is_runnable("rf103_sdr")