Large refactoring/feature commit

1. Change listen addresses to URIs
2. Break out connectionSvc to support listeners and dialers based on schema
3. Add relay announcement and lookups part of discovery service

gui/syncthing/device/editDeviceModalView.html

@@ -32,7 +32,7 @@
           <div class="form-group">
             <label translate for="addresses">Addresses</label>
             <input ng-disabled="currentDevice.deviceID == myID" id="addresses" class="form-control" type="text" ng-model="currentDevice._addressesStr"></input>
-            <p translate class="help-block">Enter comma separated "ip:port" addresses or "dynamic" to perform automatic discovery of the address.</p>
+            <p translate class="help-block">Enter comma separated  ("tcp://ip:port", "tcp://host:port") addresses or "dynamic" to perform automatic discovery of the address.</p>
           </div>
           <div class="form-group">
             <label translate>Compression</label>