Update the server and client to work with Toolbox 0.8

[soininen]

Toolbox 0.8 has been out for a while now and it bring a lot of changes, especially on spinedb_api side. While partially backwards compatible, there are some breaking changes that make the web interface unusable.

• Lock spinedb_api, spine_items and spine_engine versions to always be compatible with the spinetooblox version in requirements.txt
• Using database ids is a not an option anymore as spinedb_api now uses TempId for in-memory items. We must use unique keys instead.

I have started working on this but switching from database ids to unique keys means quite a lot of work.