use a safer default name for virtualbox

if the same vagrantfile is up'd in the same second in the same basedir
this caused a conflict,

most notably, all jenkins jobs sit in a 'workspace' directory, which
breaks if more than one job launches from the same trigger.
Add invalid character replacement

This fixes the bug seen here:
http://pastebin.com/QzWQQndK

Which would generate an Argument Error causing "vagrant up" and other such commands to fail.
provider/virtualbox: fix bad constant reference in dhcp error

refs #2454
Merge pull request #2517 from phinze/2454-fix-dhcp-error-constant-typo

provider/virtualbox: fix bad constant reference in dhcp error
Make salt bootstrap work on systems without python
Merge pull request #2525 from millerdev/master

provisioners/salt: make salt bootstrap work on systems without python
Update CHANGELOG
Merge pull request #2514 from AJCStriker/patch-1

core: add invalid character replacement in Which util
Update CHANGELOG
Merge pull request #2482 from andyfowler/safer-vbox-names

core: safer default VM names for Virtualbox
Update CHANGELOG