Add distro-specific boot libraries

This changeset adds two files (one for Ubuntu 12.04.4 LTS amd64 server,
one for Fedora 20 x86_64) containing the distribution specific
boot code.

This includes the URL for the installation ISO image, the location of the
distribution-specific preseed or kickstart files, the boot arguments,
and the sequence of keys needed to get the installer to take our boot
arguments.

The preseed or kickstart file to use is selected based on the VM_ACCESS
variable.

In the case of Fedora, VM memory is increased to 1024 MB to allow a
smooth install.

Partial-Bug: 1312764
Implements: blueprint openstack-training-labs
Change-Id: Idaf8b859e2b58036948f1a3ad077d797b3757d61