Fix documentation of Vmath Vvtvvtp function and add missing Vvtvvtm VmathArray function.

Issue/feature addressed

Documentation of the function Vvtvvtp was incorrect:

/// \brief vvtvvtp (vector times vector plus vector times vector): z = v*w + y*z

The array wrapper for Vvtvvtm was also missing.

Proposed solution

The comment should changed to

/// \brief vvtvvtp (vector times vector plus vector times vector): z = v*w + x*y

Implement Vvtvvtm wrapper and add the SIMD wrapper.

Tests

Not needed

Notes

Part Four of splitting MR!1323 feature/nonconformal into smaller MRs.

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).

Warning

On the 19.07 the code formatting (code style) was standardised using clang-format, over the whole Nektar++ code. This means changes in your branch will conflict with formatting changes on the master branch. To resolve these conflicts , see #295 (closed)