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 19 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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