mod_admin_modules: Add zmr dialog form template.

This template lists all the modules from the modules
repository server. It also comes with a text input for filtering the
modules listed in the table. Future work will be;

* Get zmr server from current Zotonic node. It is currently hard coded into the
 client code.
* Cache results on first try
* Test UI other browsers, especially mobile
* Install modules.
* Ability to refresh the data
* Make table scrollable, so items at the bottom can be accessed.