Update user guides with 0.12.0.0 GUI screenshots

Created by: SamsungGalaxyPlayer

Several guides should be updated for the latest 0.12.0.0 release.

The following need their screenshots updated:

https://getmonero.org/resources/user-guides/solo_mine_GUI.html https://getmonero.org/resources/user-guides/remote_node_gui.html

The following need to have a section for using the GUI, including screenshots:

https://getmonero.org/resources/user-guides/view_only.html https://getmonero.org/resources/user-guides/prove-payment.html https://getmonero.org/resources/user-guides/restore_from_keys.html

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