Add version number to settings dialog.

For the web app we also display the git hash.

electron/main/version.js

@@ -0,0 +1,12 @@
+import { app, ipcMain } from "electron"
+import CONFIG from "../config"
+
+export function getVersionString() {
+    let versionString = app.getVersion()
+    if (CONFIG.get("settings.allowBetaVersions")) {
+        versionString += " (beta channel)"
+    }
+    return versionString
+}
+
+ipcMain.handle("getVersion", () => getVersionString())