Refactoring substantially: `dataGenerator` plus data-driven basis computation.

[tomoleary]

In this PR we added

1. dataGenerator module that handles more complicated data generation routines that are needed for function-to-function maps.
2. Data driven computation of active subspace, and POD, more efficient computations for each, and additionally efficient computations of KLE.
3. All reduced basis computations return both an encoder and decoder.
4. And as the name of the branch suggests, we can also handle projected parameters for some PDE problems that require this :)

Yet to do:

• [ ] Rename basis to decoder, and projector to encoder to be correct in the naming convention.
• [ ] Construct regression tests for each different data generation routine.