-------------------
* add support for charts in userspace
Charts with option `show_for_users` turned on are displayed to users.
The charts has to have set some `user_field`, this filters data attributed only for the user.
* add support for multiple operation fields (separated by comma)
* improve analytics page - fix loading time, add loading overlay
* fix usage without jsonfield package installed
* Admin charts are now displayed only for users with `view_dashboardstats` permissions set on