Move offline-homes and virtualbox-mkdir to 'scripts'

Utilities are supposed to be manually invoked utility scripts, helper
programs or wrappers, and run infrequently. Both offline-homes and
virtualbox-mkdir get triggered by PAM during login, and they perform
actions by themselves, and so do not qualify as a utility
De-hardcode paths through use of 'paths' variable file
Ensure user.js generation occurs even when no alternate home exists
Move creation of symlinks for Virtualbox to pre-session