Eliminating the function also reveals a copy of the data
being made internally.

Not accessed by derived classes.

The default precision of a Writer is set 10 digits anyway
upon construction.

The extra interface is also not needed, because the
standard provided call 'precision' is doing already
the same.

It is not private, so no underscores.

Since there are no invariants maintained by the XMLInterface
nor is the access restricted, the public memeber serves
same purpose with simpler implementation.

Also fix variable naming.

writeMeshToFile is used in about 20 other places (utils)
here we use implicite conversion from string to filesystem

The fmt library happily accepts std::string without
any conversions.

Include spdlog via BaseLib/Logging.h, which
provides macro replacements for
ERR/DBUG/WARN/INFO...

XMLQtInterface::insertStyleFileDefinition

clang-tidy modernize-use-default-member-init check

Only in ERR/WARN/INFO/DBUG/OGS_FATAL and similar, not in
formatted output like xml files.

1. Changed urls to https which fixed the following error:

xsd/OpenGeoSysGLI.xsd, at line 1, column 66: Document is not a XML schema.
Error XSDError in ..., at line 3, column 194: Loaded schema file is invalid.

If this error ever pops up again try to cut the internet connection! No joke!

2. Local schema files are now copied to bin-directory during CMake configuration and package generatiion (install step).

Clang format run on near-the-header lines.

Happy New Year

This potentially saves a second copy compared to using const
reference. See Effective Modern C++, Item 41.