map object and major refactor

[tjlane]

This PR implements a new meteor.rsmap.Map object, which is a subclass of rs.DataSet that strictly holds 3 columns of:

• amplitudes
• phases
• uncertainties

This enables a much cleaner implementation of METEOR.

There are some challenges around ensuring that the child class of rs.DataSet behaves properly, and testing this is WIP.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.58%. Comparing base (b8c51b8) to head (05ad10b).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #24      +/-   ##
==========================================
+ Coverage   93.33%   96.58%   +3.25%     
==========================================
  Files           8        9       +1     
  Lines         345      498     +153     
==========================================
+ Hits          322      481     +159     
+ Misses         23       17       -6     

Flag	Coverage Δ
unittests	96.58% <100.00%> (+3.25%)	⬆️

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[alisiafadini]

Looks good. Need a scaling function that handles maps.