Pluggable admin UI and load changes

Squashed commit from `sn_manager` branch:

* Include new categories, users and groups on geostore init files.
* Now the manager UI is a pluggable extjs application like MapStore.
* MapStore changes
 * New load method (now it can load custom tools by user or group)
 * Default header and footer has been removed
 * Load custom tools if available
 * Create a map without template
* GN integration fixes
 * Use default template for the header
 * Add manager app.