Make spices easier to discover.

[klangman]

Since many people don't know that applets/desklets/actions/extensions exist that might be of value to them, I am proposing that several of the settings pages under "System Settings" should have a "Spices" tab. Under this tab a number of spices can be listed which are related to the specific settings page.

For example, in the "Effects" settings page, the "Spices" tab could show such things as "Desktop Cube", "Compiz window effect", "Burn My Windows", "Flipper", etc.

In this way, users looking for some feature that does not exist in the default Cinnamon settings might find a spice that does what they are looking for right in the most logical place for it to be found, rather than the spice being hidden away under the Applets/Actions/Desklets/Extension settings pages.

I would propose that a new "categories" section be added to the spices metadata.json file. This will define a list of places where the author thinks the spice should be listed. i.e. "categories": "effects,windows" would have the spice show up in the "Spices" tab for both the Effects and the Windows settings pages.

I believe this would be a meaningful improvement in user friendliness. Any thoughts?