add mechanism to disable module cache

[grg]

The module cache helps speed up generation by identifying when a module is generated multiple times with the same parameters and skipping duplicate generations. (This can be manually handled via clone calls. Clone is feasible within a module, but becomes difficult across modules.)

One problem right now is that the duplicate detection logic only looks at the parameters begin passed to the currently module; it doesn't consider parameters lower down in the hierarchy that may be overridden via one of the override mechanisms (e.g., command line, XML, ...).

[grg]

@steveri The module cache code was added last year. We never override parameters so it works well for us, but it could break things if parameters are overridden.

It's probably better to do one of these longer term:

• Identify when overrides are in place and disable the module cache automatically.
• Have the duplicate module detection logic look at overrides and identify if a child is being overridden.

[grg]

I actually added a test case this time 🎉

The Genesis invocation in the test includes -no_module_cache. Without it, the test fails because of the parameter override on the command line not being handled correctly by the module cache.

[steveri]

Great! Thanks for the new test.