Top bar buttons don't have tooltips

[agentydragon]

Hovering mouse on buttons doesn't have a tooltip. Clicking buttons without knowing what they do is a bit "scary" to me as a user.

Also, the "merge roam db" button might be better put somewhere else, it's not a function people will probably use frequently enough to warrant it being always visible.

(I think the same could be argued about the "open database" button)

[tangjeff0]

@shanberg started work on tooltips, and also thought about designs for moving 1. db picker and 2. merge roam from app toolbar to settings page.

[jsmorabito]

resolved in #994 thanks for the post @agentydragon ☺