Merged requested to merge CFD-Xing/nektar:feature/add-xml-checking-ci into master
As XML files are often manually generated, errors and indentation inconsistencies are often introduced. This affect readability of the files.
Add a XML linting and checking to the CI pipeline by using bash script.
 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).
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