Corrections to the Vacamole model

[pratikunterwegs]

This PR is related to #143:

1. Corrects the implementation of the Vacamole model C++ code by changing to a stricter accessor for the model infection parameter map;
2. Enables the use of rate interventions on all model infection parameters;
3. Enables the use of time-dependence on all model infection parameters;
4. Adds representative tests that check the statistical correctness of the vaccinated compartment, and that check that time-dependence works as expected on optional parameters not found in the default model.

This PR overrides #144 which restricted interventions to a smaller subset of parameters.

[pratikunterwegs]

Further correction to allow these rates to have any positive finite value; previously they were treated as proportions of the rate for unvaccinated individuals.

[pratikunterwegs]

Merging this hotfix now.