Move core interface into XAIBase.jl package

[adrhill]

Closes #151.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (9a98f97) 95.41% compared to head (c93a957) 95.04%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #154      +/-   ##
==========================================
- Coverage   95.41%   95.04%   -0.38%     
==========================================
  Files          20       17       -3     
  Lines         764      706      -58     
==========================================
- Hits          729      671      -58     
  Misses         35       35              

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[adrhill]

This introduces some breaking changes through XAIBase:

• Explanation field neuron_selection has been renamed to output_selection
• Explanation field heatmap that describes heatmapping presets has been added
• heatmap keyword argument cs has been renamed to colorscheme
• Calling heatmap(input, analyzer) will pass additional arguments and keyword arguments to the analyzer call only.

[adrhill]

Closed #151.