Ewb API: updated swagger.yaml documentation

swagger/sdrangel/api/swagger/swagger.yaml

@@ -1,6 +1,19 @@
 swagger: "2.0"
 info:
-  description: "This is the web API of SDRangel SDR software. SDRangel is an Open Source Qt5/OpenGL 3.0+ GUI and server Software Defined Radio and signal analyzer in software. It supports Airspy, BladeRF, HackRF, LimeSDR, PlutoSDR, RTL-SDR, SDRplay RSP1 and FunCube"
+  description: >
+    This is the web REST/JSON API of SDRangel SDR software. SDRangel is an Open Source Qt5/OpenGL 3.0+ (4.3+ in Windows) GUI and server Software Defined Radio and signal analyzer in software. It supports Airspy, BladeRF, HackRF, LimeSDR, PlutoSDR, RTL-SDR, SDRplay RSP1 and FunCube 
+    
+      ---
+      Limitations: 
+      
+      * In SDRangel GUI version there is no support for channel deletion. As a consequence the call to the API /sdrangel/deviceset/{deviceSetIndex}/channel/{channelIndex} returns with a status code of 501 (not implemented)
+      * The following channels are not implemented (status 501 is returned): ATV demodulator, Channel Analyzer, Channel Analyzer NG, LoRa demodulator, TCP source
+      * The content type returned is always application/json except in the following cases:
+        * An incorrect URL was specified: this document is returned as text/html with a status 400
+        * There is no API adapter in the targeted instance: message "Service not available" as text/plain is returned with a status 500. This should not happen with released code.
+      
+      ---
+
   version: "4.0.0"
   title: SDRangel
   contact: