UI: Add scene setup wizard

[cg2121]

Description

This adds a scene setup wizard where users can select
a template and easily start streaming/recording.

There are currently no templates with this, as it would make the git diff quite large.

To test out a template, move a scene collection file to the UI/data/templates/(windows, mac, or nix) folder. To test the image preview on the template page, create png image file, name it the same as the scene collection file and put it in the same folder.

Known bugs:

• Scene collection menu doesn't update when choosing template
• If the user would select the same template multiple times, there would be multiple of the same entry in the scene collection menu
• Theming issues with the System theme

If the user selects the import button, the import scenes dialog will be opened. If they select the setup on own one, the wizard just exits.

Template page:

Devices page. Users can select the devices they want to use. They can also disable the devices.

Motivation and Context

This would help users by letting them set up OBS in just minutes.

RFC: obsproject/rfcs#32

How Has This Been Tested?

Created a scene collection and then exported it to the UI data folder. With the scene wizard I then selected the template to made sure it worked.

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.

[WizardCM]

For the first screen, I vote for something more like this:

[cg2121]

Closing until OBS file containers are implemented, as that is needed for this to work properly.