Add support for setting VirtualBox video ram in definition

Make use of VBoxManage modifyvm --vram command.
single ticks prevent modifyvm command from working at least in windows and consistent with other calls
Fix install order for guest additions. They can't be installed without development essentials
Fix the dhcp clean up for Ubuntu 12.04 or newer's postinstall.sh

For more info, please see the Launchpad issue at https://bugs.launchpad.net/ubuntu/+source/isc-dhcp/+bug/910108
Added CentOS 5.6 definition for VM with puppet & chef from RPMs
Merge pull request #431 from simonmcc/master

Added CentOS 5.6 x64 definition with puppet & chef installed from RPMs
Initial commit for Fedora 18 x86_64 support against Test Compose 9 beta build.
Changes from Fedora 17:

* wget is not included, install it
* online-docs group is empty so don't bother installing it
Base Fedora install no longer includes tar or bzip2 either, essential for unpacking VirtualBox tools
Added Fedora 18 i386 support against Test Compose 9
Merge pull request #433 from juliandunn/fedora-18-support

Fedora 18 (beta) support
Forgot MD5 checksum for Fedora 18 TC9 i386.
Merge pull request #435 from juliandunn/fedora-18-i386-missing-checksum

Forgot MD5 checksum for Fedora 18 TC9 i386.
Issue #432: Handling kvm => :vm_options

Add support for network_type (network default, bridge).
Add (pre)support for volume_pool_name (but there is a bug that is preventing
this to work with fog 1.7.0).
Add some doc (about vm_options and kvm)
Merge pull request #437 from vdemeester/issue_432

Pull request for #432
Tested reduction for memory footprint to 512MB. Updated for Fedora 18 Beta RC1.
Fix spelling error: "succesfully" --> "successfully".
fix openbsd50 architecture customizations
add openbsd 5.2
Merge pull request #438 from mpapis/master

OpenBSD fixes + new templates for 5.2