mbed_app.json configured to operate on senet

To enable cayenne, edit mbed_app.json, assign pins for desired function

Example:

        "cayenne": {
            "help": "compile main_cayenne.cpp instead of main.cpp",
            "value": 1
        },
        "analog_in_pin": {
            "help": "PA_0, PA_4, PA_5",
            "value": "PA_0"
        },
        "analog_out_pin": {
            "help": "PA_0, PB_5, PB_10, PB_11",
            "value": "PB_11"
        },
        "_digital_out_pin": {
            "help": "",
            "value": ""
        }
Revision:
26:f07f5febf97f
Parent:
12:5015dfead3f2
Child:
46:a124538e2891
--- a/README.md	Tue Jun 19 14:15:24 2018 +0100
+++ b/README.md	Thu Jun 28 12:45:20 2018 +0100
@@ -147,7 +147,6 @@
 ```json
     "target_overrides": {
         "*": {
-            "target.features_add": ["COMMON_PAL"],
             "mbed-trace.enable": true
             }
      }