Create Private and Private Security policies if sharing policy allows them

setBugSharingPolicy and setBranchSharingPolicy create Proprietary and Embargoed access policies when they're enabled, but not Private or Private Security. This is a problem if a project's initial policies are pruned because they're forbidden and unused, but the project is later reconfigured to allow non-Proprietary types.

The code to create the Private and Private Security policies as part of creating a new product should be removed, and set*SharingPolicy taught to create them instead. This will depend on Ian's branch to set the sharing policies on creation.