changes to lab_virtualbox_basics

removed , after LTS
changed to Prerequisites (plural)
changed of to for
changed multi node to have a hyphen
changed a to an before x86
added an before i5
added “a” before positive result
added the before same
added the in a few places where necessary
Removed (not necessary)
removed “unless know what you are doing”
added “unless you are an advanced user”

Change-Id: Icaa5a92e1f3685c6aa5626b3d37044219757ed20
Merge "changes to lab_virtualbox_basics"