Set version to 2.3.0
templates: media_resources: split _list from _wrapper
remove obsolete templates
sass: remove stray pixel line below .ui-tabs
sass: fix nested .rounded .ui-containers
sass: better css fix for nested .ui-container.rounded > .ui-container.bright etc.
sets/entries: fix nesting of .ui-containers; consistent layout templating
container nesting: fix /filter_set
container nesting: fix /contexts
container nesting: fix /entries/edit_multiple
container nesting: fix /my
container nesting: fix /explore
container nesting: fix /custom_urls
container nesting: fix /import
container nesting: fix /media_resources
container nesting: fix /media_entries
container nesting: fix /permissions
container nesting: fix /responsibilities
container nesting: fix /search
container nesting: fix /media_resources/browse