v0.50.0-beta release

This is a beta release and can contain serious bugs. Use for evaluation only.

• brand new external REST API called ETAPI
• removed username from authentication, only password is now needed
• removed setting password in the initial setup to speed up the process and avoid confusing users, it's possible to set it up later
• added possibility to reset password (thus losing protected notes, if any) from Options.
• as a result of above, typical "new document" setup is just two-click process without having to enter username & password
• optimized sync protocol which can now in some cases halve the sync/time
• unified Jump-To and quick search behavior with regards to hoisting and opening in a new tab, #2483
• search immediately when user chooses "full search" from Jump To dialog, #2483
• make whole text/code detail clickable to improve UX, add placeholder to empty code notes
• print should include promoted attributes, #2550
• add #shareRoot label to define an "index" note, closes #2567
• initial theme is chosen based on OS settings, #2516