Canvas: Separate page for Export

[neoneye]

Currently the Canvas menu is a mix of settings UI and export UI.

The UI becomes more legible by splitting it up into two separate menus, like this:

With the typical Apple "Share" icon for the export menu, and a "Gear" icon for the settings menu.

The export UI can have buttons like this:

• Save to photos, 2048x2048.
• Save to photos, 8k.
• Export to PDF, with pdf options.
• Export to SVG, with svg options.
• Export to a zip containing PDF+SVG+Hi resolution image.