ACP quick actions (#6374)

* ACP quick actions

- Moved restart, build & restart, and logout into separate buttons
- Moved buttons on mobile into the side menu
- Added version and upgrade alert to header / mobile menu
- Moved version checking to server-side with a cache for rate limiting
- Changed "reload" translations to "rebuild and restart"

* Change info alert to black-on-white to match focused search bar

* Fix tests

* Fallback for failed fetch of latest version

src/admin/versions.js

@@ -0,0 +1,55 @@
+'use strict';
+
+var semver = require('semver');
+var request = require('request');
+
+var meta = require('../meta');
+
+var versionCache = '';
+var versionCacheLastModified = '';
+
+var	isPrerelease = /^v?\d+\.\d+\.\d+-.+$/;
+
+function getLatestVersion(callback) {
+	var headers = {
+		Accept: 'application/vnd.github.v3+json',
+		'User-Agent': 'NodeBB Admin Control Panel/' + meta.config.title,
+	};
+
+	if (versionCacheLastModified) {
+		headers['If-Modified-Since'] = versionCacheLastModified;
+	}
+
+	request('https://api.github.com/repos/NodeBB/NodeBB/tags', {
+		json: true,
+		headers: headers,
+	}, function (err, res, releases) {
+		if (err) {
+			return callback(err);
+		}
+
+		if (res.statusCode === 304) {
+			return callback(null, versionCache);
+		}
+
+		if (res.statusCode !== 200) {
+			return callback(Error(res.statusMessage));
+		}
+
+		releases = releases.filter(function (version) {
+			return !isPrerelease.test(version.name);	// filter out automated prerelease versions
+		}).map(function (version) {
+			return version.name.replace(/^v/, '');
+		}).sort(function (a, b) {
+			return semver.lt(a, b) ? 1 : -1;
+		});
+
+		versionCache = releases[0];
+		versionCacheLastModified = res.headers['last-modified'];
+
+		callback(null, versionCache);
+	});
+}
+
+exports.getLatestVersion = getLatestVersion;
+exports.isPrerelease = isPrerelease;