GTK App Fixes

[mmstick]

This PR will work to address all open issues regarding the GTK front end, and then some, with additional abstraction work to minimize the GTK work.

• Closes Local build instructions #18
• Closes "Select all" checkbox should be bound to the selection state of the drives #19
• Closes .back → .back-button class #20
• Closes Add "Hash:" label before the hash combobox #21
• Closes Move spacing from CSS to properties #23
• Closes Remove borders on drive selection #24
• Closes Improve margins for chooser_container  #25
• Closes Add margins to stack #26

[jackpot51]

I think at line 314 in gtk/src/app/state.rs, the device list is not filtered based on the checkbutton. Is that true?

EDIT: I fixed this here: 10faca1

[jackpot51]

The hash gets truncated now that that Hash: label is before the dropdown. Perhaps we should increase the minimum size of the window?

[mmstick]

Yeah, it should default to a size that fits the complete hash.

[mmstick]

Unsure on how to set a minimum size at the moment.

[jackpot51]

That's ok, I think it is fine as-is

[jackpot51]

Since this is an improvement over how it was before, I will merge so it makes it into the next ISO. Further issues may be filed concerning the master branch