Update of Parareal algorithm

Issue/feature addressed

Update to Parareal:

1. Add convergence criteria to Parareal loop.
2. Fixed Hdf5 IO Issue (see MR !1512 (merged)).
3. Generalize the use of GetSpaceComm() communicator (see MR !1518 (merged)).
4. MeshGraph is updated to create coarse partition files (see MR !1516 (merged)).
5. Modify SessionReader to read restart/exact solution files parallel-in-time (see MR !1521 (merged)).
6. Add new interpolation function (see MR !1514 (merged)).
7. Remove m_root to avoid potential confusion (see MR !1515 (merged)).
8. Remove unused function SetUpXmlDoc (see MR !1513 (merged)).
9. Update to Parareal file output (See MR !1517 (merged)).
10. Add parallel-in-time capabilities to FieldConvert (See MR !1520 (merged))

Tests

Notes

Please add any other information that could be useful for reviewers.

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)