Feature/tidy up basis points

Issue/feature addressed

This is a tidy-up of Basis and Points classes and subclasses.

Proposed solution

• Add a laginterpderiv function in Polylib.cpp
• Remove LagrangeInterpolant, LagrangePoly, and LagrangePolyDeriv member function in PolyEPoints.h and GaussPoints.h
• Explicitly delete default and copy constructor when necessary
• Remove unnecessary header file declaration
• Use size_t instead of unsigned int
• Add final keyword to private virtual function
• Remove unused commented code
• Add a ASSERTL0 error to incomplete member function in BLPoints.cpp and FourierSingleModePoints.cpp

Implementation

Tests

Suggested reviewers

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Notes

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Checklist

• [ ] Functions and classes, or changes to them, are documented.
• [ ] User guide/documentation is updated.
• Changelog is updated.
• [ ] Suitable tests added for new functionality.
• Contributed code is correctly formatted. (See the contributing guidelines).
• License added to any new files.
• [ ] No extraneous files have been added (e.g. compiler output or test data files).