[WIP] Added nemo-tags v1.0 plugin

[DIMFLIX]

This PR adds nemo-tags extension - a powerful tagging system for Nemo File Manager.

Source repository: https://github.com/meowrch/nemo-tags

Note: This directory contains the built version of the extension.
The source code with modular structure is maintained in the upstream repository.

[mtwebster]

I'm not sure you can do enough with the extension system to make this sort of thing really work. There are also already quite a few ways to organize and differentiate items - pinning, favorites, folder colors. It also makes use of emblems (which is another extension), that are not necessarily displayed in all situations.

Also, the versioning should be in line with other extensions, and the real source code should live here. If that's not possible, this should be probably be maintained separately.

A few real observations from trying it:

• Nemo crashes after a while of using this extension, navigating in and out of folders. I don't have a reliable trigger for this.
• The location bar always shows.. this is just taking up space in the file view. Again, as an extension you don't have much choice.
• You're creating a separate folder heriarchy to display these, and their path shows. I think this sort of implementation detail shouldn't be exposed.

Ideally you click on a color button somewhere, and your pathbar changes to a button with the color dot, showing all of your tagged files in the view as files, not as symbolic links. It should work like the Favorites or Recent locations.