Add apt-get update, su -c, GT.M x86_64 shared lib support

For cloud installs apt-get update needs to be ran before we install git,
build-essentials, etc.

Move most file creation and program execution to run su $instance -c so
the commands are ran with the instance user and not as root

Add GT.M shared libary support for x86_64 as by default gtminstall will
only install the shared library version and not have the programs in
$gtm_dist

Use gtmver environment variable for cmake build name generation

Change-Id: Ide4aaa433eace00bdcccfbfc7fe03493069f91eb
Fix hardcoding of vagrant username

Racksapce and other cloud providers don't use a vagrant username, which
will cause the autoInstaller script to throw errors and not perform the
intended actions.

Change-Id: Ie9d0aaaa1b4aa04b3a85c8662b2e27c2cc9ac5f4
OSEHRA-Id: http://issues.osehra.org/browse/VAF-147
WIP: Add support for Rackspace cloud

Add support Rackspace cloud into Vagrantfile using environment variables
so users don't have to modify the Vagrantfile to enter their credentials

Add documentation explaining the usage of environment variables and how
to setup environment to create a Rackspace Cloud VM.

Change-Id: I10dec3a47aa2fa5368097cce489ab6c43a31331e