Remove ServerConfig; Add Signup logic class

- ServerConfig seems too specific to Vector, but we can always add it back later.
- Signup.js contains all the logic for determining what to show which was
  previously in UI components.

src/Signup.js

@@ -0,0 +1,49 @@
+"use strict";
+var MatrixClientPeg = require("./MatrixClientPeg");
+var dis = require("./dispatcher");
+
+class Register {
+
+}
+
+class Login {
+    constructor(hsUrl, isUrl) {
+        this._hsUrl = hsUrl;
+        this._isUrl = isUrl;
+        this._currentFlowIndex = 0;
+        this._flows = [];
+    }
+
+    getFlows() {
+        var self = this;
+        // feels a bit wrong to be clobbering the global client for something we
+        // don't even know if it'll work, but we'll leave this here for now to
+        // not complicate matters further. It would be nicer to isolate this
+        // logic entirely from the rest of the app though.
+        MatrixClientPeg.replaceUsingUrls(
+            this._hsUrl,
+            this._isUrl
+        );
+        return MatrixClientPeg.get().loginFlows().then(function(result) {
+            self._flows = result.flows;
+            self._currentFlowIndex = 0;
+            // technically the UI should display options for all flows for the
+            // user to then choose one, so return all the flows here.
+            return self._flows;
+        });
+    }
+
+    chooseFlow(flowIndex) {
+        this._currentFlowIndex = flowIndex;
+    }
+
+    getCurrentFlowStep() {
+        // technically the flow can have multiple steps, but no one does this
+        // for login so we can ignore it.
+        var flowStep = this._flows[this._currentFlowIndex];
+        return flowStep ? flowStep.type : null;
+    }
+}
+
+module.exports.Register = Register;
+module.exports.Login = Login;