Update for general cleanliness and packaging

The commit messages are pretty clear, but for simplicity's sake, this pull request:
* Deletes the old ``tmxgta_X`` and renames the current version to ``tmxgta-backend``
* Updates ``tmxgta`` for using the ``-backend`` script
* Moves all of the files out of the redundant file hierarchy

Following these changes, a very simple -git PKBUILD can be made in order to have this function as an [installable package](https://github.com/HalosGhost/Packages/blob/master/tmxgta-git.PKGBUILD). The package linked to is a reference package that should work perfectly with the changes this pull request makes.