Remove commented lines in vbox-guest-additions

Signed-off-by: Kris Hicks <krishicks@gmail.com>
Remove more old files

Signed-off-by: Kris Hicks <krishicks@gmail.com>
Update bin/build-aws usage text

Signed-off-by: Kris Hicks <krishicks@gmail.com>
Update BuildBoxes.md

Signed-off-by: Kris Hicks <krishicks@gmail.com>
Update packer build command invocation

Use a subshell to properly evaluate -var arguments

Signed-off-by: Kris Hicks <krishicks@gmail.com>