Convert init.d script to upstart

[Gediminas Paulauskas]

An upstart init script needs to be written to replace /etc/init.d/schooltool

A new script /usr/sbin/schooltool should be created that supports multiple instances, configured in file /etc/default/schooltool, so that the following commands are interchangeable:

  $ sudo start schooltool
  $ sudo schooltool start

The ``schooltool`` command should take an optional instance argument, to act only on one server:

  $ sudo schooltool restart standard

It may or may not use the upstream scripts, make-schooltool-instance and start-schooltool-instance, but they need new options (LP: #906373)