Break the fs package up into smaller parts.

The purpose of this is to make it easier to maintain and eventually to
allow the rclone backends to be re-used in other projects without
having to use the rclone configuration system.

The new code layout is documented in CONTRIBUTING.

fs/log/syslog.go

@@ -0,0 +1,16 @@
+// Syslog interface for non-Unix variants only
+
+// +build windows nacl plan9
+
+package log
+
+import (
+	"log"
+	"runtime"
+)
+
+// Starts syslog if configured, returns true if it was started
+func startSysLog() bool {
+	log.Fatalf("--syslog not supported on %s platform", runtime.GOOS)
+	return false
+}