Add 2d projection demo and tests

Issue/feature addressed

Previously no test for 2d h-type convergence.

Proposed solution

Add a demo and test of h-type convergence of a 2d continuous Galerkin projection.

Implementation

Following MR !1738 (merged), the 1D Demos/MultiRegions/Project.cpp has been renamed to Project1D.cpp, and Project2D.cpp has been added, which can use either triangle or quadrilateral elements.

Tests

Triangle and quadrilateral tests added.

Suggested reviewers

@dmoxey

Notes

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).