staking: Add various data views

[JoeGruffins]

As stated in the recent proposal.

I assume this includes a screen to view the status of all tickets.
@buck54321 Please comment on what else this entails.

[buck54321]

Viewing current ticket statistics would be good. We'll need a way to see if any tickets are expired or missed a vote so they can be revoked too. Ideally the revocation process could be automated away, possibly via user settings, but click-to-revoke is a reasonable first step in that direction. Which also means we'll need a user settings screen too for things like setting transaction fees and UI preferences.

I'm not super interested in doing historical data plots just yet. The hardest part might be getting good looking tables in Qt. I've avoided tables so far, but these data view will be pretty dense, so little tables may be the only way to do it.

[JoeGruffins]

Ok, so for this issue I'd like to make two screens: a settings screen and a tickets screen.

I think the tickets screen should be a pager with one ticket per page. It should include:

• ticket amount
• pool's url
• time bought
• status
• revoke button if revocable
• progress bar (like dcrdata) that shows time til mature status and switches to time til expiration, then time til spendable

The settings screen should have:

• voting choice
• revoke all tickets, if applicable
• theme?
• default fee
• ???

I would like to start on the tickets screen if that's ok.

[JoeGruffins]

I think I'll break this up into one issue/pr per screen