Start adding wayland support.

This merge will start the process of adding support for the wayland windowing system. @aryak1 is working on something similar however there are issues with his implementation that are yet to be addressed so I made a version which I think is suitable.

I have created a function called cp2cb which should be used in favour of plain xclip or wl-clipboard. If you need unique functionality for cp2cb (like in dm-maim) create a local version of cp2cb under a new name with different functionality.

Everything in x11 has been tested except for dm-maim, please test it if possible. Nothing in wayland has been tested but reading the man pages what I've written should work fine. That being said please test if you have a wayland system, I need some feedback on these changes.

I plan to add more wayland functionality into the script along with @aryak1 (if he is interested) and with others who are interested in wayland. I personally don't use wayland but I could see it being very useful to support it going into the future. At some point I may test some of these scripts on wayland but as of right now I need wayland testers. Maybe the README.md could be updated with that information?

Hopefully this merge will be accepted, I think it is extremely useful and in general it just makes sense. I plan in the future to address some other issues as well, such as the dmenu variable mentioned in an issue I wrote awhile back.