Feature/52 refactor inversion solution

[chrisbc]

reference #52 here we have:

• refactored the main *Solution classes/pacakges to make things more maintainable
• refactored the API to make it easier to remember
• improved API docs
• removed old API methods

[codecov]

Codecov Report

Attention: Patch coverage is 92.87532% with 28 lines in your changes missing coverage. Please review.

Project coverage is 93.59%. Comparing base (cd50f24) to head (cf9904c).
Report is 1 commits behind head on pre-release.

Files with missing lines	Patch %	Lines
solvis/solution/composite_solution.py	78.26%	5 Missing ⚠️
solvis/solution/typing.py	85.29%	4 Missing and 1 partial ⚠️
...ault_system_solution/fault_system_solution_file.py	81.25%	2 Missing and 1 partial ⚠️
...ult_system_solution/fault_system_solution_model.py	92.30%	2 Missing and 1 partial ⚠️
...ion/inversion_solution/inversion_solution_model.py	94.73%	3 Missing ⚠️
solvis/solution/solution_surfaces_builder.py	62.50%	2 Missing and 1 partial ⚠️
...ion/fault_system_solution/fault_system_solution.py	96.22%	0 Missing and 2 partials ⚠️
...tion/inversion_solution/inversion_solution_file.py	90.90%	1 Missing and 1 partial ⚠️
.../solution/inversion_solution/inversion_solution.py	98.27%	1 Missing ⚠️
solvis/solution/named_fault.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##           pre-release      #53      +/-   ##
===============================================
+ Coverage        91.57%   93.59%   +2.01%     
===============================================
  Files               22       23       +1     
  Lines             1305     1373      +68     
  Branches           114       89      -25     
===============================================
+ Hits              1195     1285      +90     
+ Misses              86       63      -23     
- Partials            24       25       +1     

Flag	Coverage Δ
unittests	93.59% <92.87%> (+2.01%)	⬆️

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