Extract Legacy Installer

* Legacy installers are now in their own files, simplifiying the
start scripts (which reflect a different concern).
* Installation documentation has been enhanced.
* Batch files have been refactored to be a little more readable.
Ensure that the launchd dir exists on OSX

This stops the install failing on a clean OSX install
Merge pull request #1482 from benbc/2.0-legacy-installer

2.0 legacy installer