Autotiling 1.7

Added a line to remove workspaces tmp file, if no --workspaces specified. The simple txt file stores the --workspaces flag content, to let the panel know which workspaces to mark with the "a" letter.

This will only be useful for use the script with nwg-panel, but not with full nwg-shell. The latter uses its own version of the autotiling script, which also allows just single instance, and can be started with exec_always. I decided not to include it into this version, due to the additional psutil dependency.