Renamed stdout for diffusion/reaction advancement.

Issue/feature addressed

Diffusion and reaction advancement are printed wrongly in stdout.

Proposed solution

Rename the stdout(s) for diffusion and reaction advancement appropriately.

Implementation

Changed "Advect. advancement" to "Diffuse./React. advancement" (L594, L600)

Tests

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).

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)