implement unit tests with jest. configure it to match our specific needs. atm no icons can be imported and have therefor been commented out in the component to be tested

change label from 'date' to 'year' since it seems to be more descriptive. thank you for pointing this out, Mani

#55

init panel order config: 1st draft. init npm publishing. minor corrections regarding indents and prop order

refactored toggleBar to toggleIndex / toggleFilter according to window size. toggle switches at 1100px

group contents and metadata in one single panel. exchnage meta by annotation panel and adjust splitter ratios

update pkgs. extend panel config. rewrite toggle mechanism and event emitters. fix stylings for the panels

rename 'pagelabel' to 'itemlabel'; revert former changes in regards to 'imgeurl' due to wrong branch; expand first knot in tree by default which holds the actual item selected; dynamic collection title in tree instead of literal one

rename 'pagelabel' to 'itemlabel'; revert former changes in regards to 'imgeurl' due to wrong branch; expand first knot in tree by default which holds the actual item selected; dynamic collection title in tree instead of literal one

cf. #26