admin-ui: Refactor the selection/deselection functionality

Also, the way the actions get enabled or disabled is modified.
admin-ui: Update buttons and modals
admin-ui: Overall refactor of javascript code

Also, the files extra.js and tables.js are merged in the former.
admin-ui: Style modifications
Merge branch 'feature-admin-ui' into feature-admin
admin: Remove unnecessary template tags
admin: Show only initialized values in users

The moderation_policy field is not initialized for unmoderated users,
which means that it must not be shown for these users.
admin: Minor fix in users
admin: Update VM list
admin: Add Volume list page
admin: Add Network list page
admin: Add IP list page
admin: Update Project list page
admin: Add user group list page