Added post-install script, and start UserBootscript again.

* This is the final missing piece of the former boot process.
* Removed the unused Bootscript, and Bootscript.cd files.

data/launch/system

@@ -70,6 +70,11 @@ service x-vnd.Haiku-power_daemon {
 	legacy
 }
 
+job post-install {
+	launch /bin/sh /system/boot/PostInstallScript
+	if file_exists /boot/system/settings/fresh_install
+}
+
 target login {
 	job x-vnd.Haiku-autologin {
 		launch /system/bin/autologin

data/launch/user

@@ -17,6 +17,10 @@ target desktop {
 		}
 	}
 
+	job user-bootscript {
+		launch /bin/sh /boot/home/config/settings/boot/UserBootscript
+	}
+
 	job create-installer-link {
 		# When run from a read-only medium a.k.a. live desktop
 		if {