Add Gio interface

[hyhydra0]

This adds the GIOUI interface to the application.

This PR implements the following:

• Welcome page
• Restore wallet page (verify seed screen, spending password screen, success screen)
• Create Wallet page (spending password screen, seed backup screen, verify seed screen, success screen)
• Overview page

Note: the pin tab on the spending password container has not been implemented yet

Fixes #441

[metaclips]

I get this while running gio interface. We are using masters branch of dcrlibwallet so we really dont need any use of the app package.

[metaclips]

I get this UI while testing. We are currently using a new mockup which fyne follows, you can use that as a reference as create/restore page and receive page has been implemented. Please move to multi wallet feature of dcrlibwallet.

[beansgum]

I'm getting this cut off. I'm running on macOS, the cut off stays the same after resizing the window several times. I also cleared my app data and started fresh and I got the same result.