Remove lucid code and installation of Brightbox ruby

This simplifies our build scripts, removing all the code to build lucid
machines, removing the installation of a custom ruby and making the
installation of virtualbox tools dependent on detecting a virtualbox VM.
Update to ubuntu 12.04.5
Prep Makefile for building VMWare Fusion box
Use the virtualbox iso provided by VeeWee
Install vmware tools if needed
Remove generic-named boxes after build
Enable automatic kernel modules on vmware

Required moving the iso mount to /mnt/cdrom, otherwise build fails
because it tries to write to /mnt/hgfs which is within where the
original tools ISO was mounted.
Clarify why we reset the ruby alternative
Merge pull request #9 from alphagov/remove-lucid

Remove lucid, update Precise to 12.04.5