Add an cmd option --restart

[LintaoAmons]

Sometimes, I found after disconnected from a monitor or changed the orrangement of the displays, warpd can't adjust itself correctly which requires a restart of the process.

I'm currently using htop to find the existing process and to kill it, then restart the warpd process again which is quite cumbersome.

So if we could have some command line option like --restart should be quite helpful!