Revert "Proper signal handling in monitor process"

This reverts commit 33e9a88b56395130873a4052381baa7d90486779.
Revert "Use a monitor process to handle panics and restarts (fixes #586)"

This reverts commit 10f071325726e8de1d44ec9ea1a7a9741f885c6d.

Conflicts:
	cmd/syncthing/monitor.go