Most of the current .clang-tidy contained checks:
google-explicit-constructor
google-readability-braces-around-statements
modernize-loop-convert
modernize-use-default-member-init
modernize-use-emplace
modernize-use-using
readability-braces-around-statements
readability-else-after-return
readability-named-parameter
*readability-namespace-comments
*readability-inconsistent-*
readability-redundant-member-init
readability-simplify-boolean-expr
readability-string-compare
*explicit-conversions*

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

Now includes the copyright message and the version info with git hash.

Clang format run on near-the-header lines.

Happy New Year

* some arguments that are mutually exclusive are checked
* --mx now works together with --nx etc.

FileIO -> MeshLib::IO.

In order to make OGS more modular:
- The {read/write}Mesh{From/To}File.{h,cpp} are moved from FileIO to MeshLib/IO.
- The FileIO/Legacy folder was moved to MeshLib/IO/Legacy.
- Include paths are changed according the changes above.

When the current commit is also a tag then the version is the tag name,
e.g. "6.0.1". When the current commit is not a tag then the ogs version
is the last tag + number of commits since then + current commit short
hash, e.g. "6.0.1-140-g80ac475".

This info is available in BaseLib::BuildInfo::git_describe. Use it to
uniquely set the OGS version.