Revert to_s for institutional_group
test: add test for setting of institutional group meta data (rspec/capybara)

also moved existing meta_data_spec in new subfolder
move .level-up overlay template from media_sets to media_ressources; use it; fix styles
refactor/simplify styles (grid mode)
move .level-up overlay template from media_sets to media_ressources; use it; fix styles
(resources container view)
move and adjust javascript and client templates
sass: fix small visual bug in overlay arrows

showed a grey line on retina displays, no overlayed with a box-shadow
add a test for old and new overlays
test: add scenario for plain listing of resources