Refactoring imageRouter to modularity

This should make the imageRouter more modular and easier to extent. Also
a lot of code duplication was removed which should simplify maintenance
in future.

In the new setup we only need to provide a new module file which exports
a function called `uploadImage` and takes a filePath and a callback as
argument. The callback itself takes an error and an url as parameter.
This eliminates the need of a try-catch-block around the statement and
re-enabled the optimization in NodeJS.

Signed-off-by: Sheogorath <sheogorath@shivering-isles.com>

lib/web/imageRouter/filesystem.js

@@ -0,0 +1,18 @@
+'use strict'
+const url = require('url')
+
+const config = require('../../config')
+
+exports.uploadImage = function (imagePath, callback) {
+  if (!imagePath || typeof imagePath !== 'string') {
+    callback(new Error('Image path is missing or wrong'), null)
+    return
+  }
+
+  if (!callback || typeof callback !== 'function') {
+    callback(new Error('Callback has to be a function'), null)
+    return
+  }
+
+  callback(null, url.resolve(config.serverurl + '/', imagePath.match(/^public\/(.+$)/)[1]))
+}