Added saving & loading of current mode in localStorage
Refactored mode API to be cleaner
Added "work attribution" mode: it allows to pre-define flags for composer/lyricist (in people's list) to assign later;
Refactored flag toggling API
Added lists-by-mode visibility
Added working "go" button for work attribution mode
Refactored current UUID / entity extraction API in separate function
Failsafe mechanism for URL entity regexp failing
"Go" in work attribution mode, in the middle of edit, doubles as "Enter edit" form submission button. Thus it's possible to enter edits faster by just repeatedly clicking "Go" all the time after pre-setting attributions.