Sanitize user input

[PzYon]

E.g. Trim texts (especially titles). Consider adding a "sanitizeItem" or something function to
https://github.com/PzYon/engraved/blob/master/server/src/db/DbService.ts:

• call it for add and update
• trim title and desc
• maybe do other things
• maybe even consider adding this to shared...?

While we are already at it, we might as well cleanup that class a bit. E.g. updateItem should not return promise of any, etc. There might be some other things, as apparently the typing for mongodb have been improved.