Support source control of mapping configuration

[isc-tleavitt]

The configuration that determines the mapping between InternalName and filesystem structure should itself be source controlled. (And changes to it must be reflected as a first priority in pull event handlers/import/etc.)

In a package manager context, this is irrelevant; module.xml defines the mapping.

[isc-pbarton]

Other configuration settings that should be source controlled:

• Pull Event Class
• % Replacement on Export
• Mappings
• Production Decomposition

[isc-tleavitt]

This should also support parameter expansion of the environment as implemented in #124

[isc-pbarton]

Resolved by #469