MOLE v2.0.0: C++ Readiness

### Objective
Bring the C++ implementation into compliance with the MOLE 2.0
API, numerical behavior, testing, documentation, and packaging standards.

### Implementation Plan

- [x] Adopt new CPP software organization into the directory structure in Figure 1 (below)
- [x] Implement MOLE Errors handling and reporting system.
- [x] Implement C++ regression tests for the MOLE Errors module and use examples for documentation
- [x] Implement MOLE Grid classes and related data structures
- [x] Implement C++ regression tests for the MOLE Grid classes + Error handling/tracking, and basic examples for documentation
- [x] Implement MOLE sparse utility that are a requirement for MOLE operators and boundaries.
- [x] Implement C++ regression tests for the MOLE utilities (sparse matrix operations) and integration with previous development
- [ ] Implement MOLE Operators updates using the new MOLE 2.0 syntax VOut = operator(order, Grid), where operator = divergence, gradient, laplacian and curl (when applicable)
- [ ] MOLE operator Unit and regression tests pass
- [ ] Implement MOLE Boundary class
- [ ] Implement C++ regression tests for the MOLE Boundary classes and integration with previous development. and basic examples for documentation
- [ ] Refactor MOLE v1.2 examples to use MOLE 2.0 syntax
- [ ] Results agree with the reference implementation
- [ ] Deprecated 1.x interfaces are removed or documented
- [ ] Installation and packaging instructions are current
- [ ] Language-specific documentation is complete

Individual implementation tasks should be created as sub-issues
and linked below.

**Keep-open request**
- [X] I am requesting maintainer review for `keep-open`.

Reason:
The MOLE v2.0.0 C++ implementation will require several steps to complete. We need to keep this issue open to track progress.

**Figure 1.** MOLE 2.0 - CPP software directory distribution