Autosave sessions in jbrowse-web IndexedDB database to make it easier to access old sessions

[cmdcolin]

users can run out of local storage limits with large sessions, and the system can also forget your recent sessions fairly easily

On desktop, we have autosave, this basically ports the same concept to web by using indexeddb which has much higher storage limits

Fixes #3575
Fixes #3392
Fixes #1445
Fixes #4690
Fixes #1384

standardizes on saving sessions by ID, which is a good indication of being the same exact session, instead of name, which is just the same by happenstance in most cases

[cmdcolin]

some todo's from meeting with @garrettjstevens

• add mouseover date/time
• move menus to the session model
• create concept of "favorites" on the recent sessions table. this would supplant the current concept of 'saved sessions'
• try not to load all data using getAll...just get session name/createdAt for example, and maybe limit total number of sessions

[cmdcolin]