refactor: use dataPath variable as given in file config (#1118)

* Actually use path variables as given in default config

* Drop paths.content, avoid populating the global WIKI object

server/controllers/upload.js

@@ -11,7 +11,7 @@ const sanitize = require('sanitize-filename')
  * Upload files
  */
 router.post('/u', multer({
-  dest: path.join(WIKI.ROOTPATH, 'data/uploads'),
+  dest: path.resolve(WIKI.ROOTPATH, WIKI.config.dataPath, 'uploads'),
   limits: {
     fileSize: WIKI.config.uploads.maxFileSize,
     files: WIKI.config.uploads.maxFiles