Switch the library to ArrayRef

[akern40]

This is a large PR that repeatedly does a simple process: find locations of &ArrayBase and replace it with &ArrayRef, then remove any unused generics. The only change that isn't in this theme is for EigGeneralized, for which we need a new trait to provide a tuple-friendly implementation (see #412 for more details).

Closes #412

[codecov]

Codecov Report

❌ Patch coverage is 72.15190% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.35%. Comparing base (edff246) to head (729edc0).
⚠️ Report is 14 commits behind head on master.

Files with missing lines	Patch %	Lines
ndarray-linalg/src/tridiagonal.rs	14.28%	18 Missing ⚠️
ndarray-linalg/src/krylov/householder.rs	66.66%	3 Missing ⚠️
ndarray-linalg/src/solveh.rs	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #415      +/-   ##
==========================================
- Coverage   87.65%   87.35%   -0.31%     
==========================================
  Files          65       65              
  Lines        3895     3937      +42     
==========================================
+ Hits         3414     3439      +25     
- Misses        481      498      +17     

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