Removed node-wot but kept centralised TD store

I had intended to store a ConsumedThing for each Thing, in
a module in the store. Until that is possible (will require some
more attention to dependency management) I will just store
the TDs instead.

This commit includes a lot of the code I wrote for node-wot use,
but without any dependence on node-wot.

webapp/src/wot-client.js

@@ -0,0 +1,37 @@
+import axios from "axios";
+
+export const wotStoreModule = {
+  namespaced: true,
+  state: () => ({
+    thingDescriptions: {},
+    servient: null,
+    helpers: null
+  }),
+  mutations: {
+    addThingDescription(state, { thingUri, thingDescription }) {
+      state.thingDescriptions[thingUri] = thingDescription;
+    },
+    removeThingDescription(state, thingUri) {
+      delete state.thingDescriptions[thingUri];
+    },
+    removeAllThingDescriptions(state) {
+      state.thingDescriptions = {};
+    }
+  },
+  actions: {
+    async start() {
+      // Set up thing client - not currently used.
+    },
+    async fetchThingDescription({ commit }, uri) {
+      // Fetch the thing description from the given URI and consume it
+      // NB this should only be called once, or we'll duplicate effort.
+      // Deduplication should be done elsewhere.
+      let response = await axios.get(uri);
+      let td = response.data;
+      commit("addThingDescription", { thingUri: uri, thingDescription: td });
+    }
+  },
+  getters: {}
+};
+
+export default wotStoreModule;