Solvis

Added
- geometric surface projections from fault sections
- 3D distance calculation for both crustal and subduction subduction faults systems
- new_solution helper function in InversionSolution class (used by solvis.new_sol)
- add some performance tests using `pytest.mark.performance`
- helper functions for dip-direction, bearing etc in geometry package

Changed
- `pytest.mark.slow` for some potentially slow tests
- surfaces now use LineString (not Polygon) for Faults with dip-deg=90. eg Fowlers
- module package refactoring

Changed
- refactored project structure for packaging
- changelog format for bump2version

Added
- poetry with: pytest, coverage, tox, flake8, mypy, black, isort, bump2version

Changed
- improvements to mfd_hist