clean up web.xml servlet context parameters
Merge branch 'frontend-refactoring'
split CSS to separate stylesheets by components
JS apps are loaded as ES6 modules
replaced logo in PNG format by SVG
modified apps to use newly created custom event JS classes
modified ShowGraphApp to use newly created Header and Navbar JS classes
Repaired two selenium tests
added userMenu functionality to UploadFilesApp
reworked LoginPopup and RegisterPopup to extend newly created Popup JS class
reworked UploadFiles page to use extended App JS class
replaced jQuery by native JS wherever possible
reworked all jQuery-backed AJAX calls to use AJAX JS class
minor improvements
modified Upload screen to dynamically display/hide user's private diagrams on log in/out
elements' visibility is controlled by body class which is set based on user's login state
replaced select field by radio inputs (better UX)
updated jQuery
Added possibility to upload raw JSON (front-end -- back-end JSON)
Added remove confirmation dialog
minor frontend changes
UI for removing diagrams from database
frontend cleanup
reworked upload screen
joined load graph and start visualization steps on uploadFiles page. Removed saving uploaded file to file system.
dropped some unused functionality, merged DefaultPage with UploadFiles servlet
rebranding
moved frontend code to directories following Maven convention, dropped libraries that are managed by Maven