Add option to set num_factories in OSG_autoconf

[mmascher]

Is your feature request related to a problem? Please describe. The num_factory knob allows factory operators to set the number of factories. However, OSG_autoconf is not equipped to handle this knob. We should add the necessary code to allow change it.

Info (please complete the following information):

• Priority: high
• Stakeholders: FactoryOps
• Components: factory