Renamed property in configuration to measured quantity

According to our discussion that the device properties are a name
that the users can't handle immediatly, we already made the
renaming to measured quantity in the device page.

The remaining notions of "property" in the configuration page
are now resolved.

pages/configurations/_id.vue

@@ -227,7 +227,7 @@ permissions and limitations under the Licence.
                       v-model="configuration.location.latitude"
                       :devices="getAllDevices()"
                       device-select-label="Device that measures latitude"
-                      property-select-label="Property for latitude"
+                      property-select-label="Measured quantity for latitude"
                       :readonly="readonly"
                     />
                   </v-col>
@@ -236,7 +236,7 @@ permissions and limitations under the Licence.
                       v-model="configuration.location.longitude"
                       :devices="getAllDevices()"
                       device-select-label="Device that measures longitude"
-                      property-select-label="Property for longitude"
+                      property-select-label="Measured quantity for longitude"
                       :readonly="readonly"
                     />
                   </v-col>
@@ -245,7 +245,7 @@ permissions and limitations under the Licence.
                       v-model="configuration.location.elevation"
                       :devices="getAllDevices()"
                       device-select-label="Device that measures elevation"
-                      property-select-label="Property for elevation"
+                      property-select-label="Measured quantity for elevation"
                       :readonly="readonly"
                     />
                   </v-col>