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

Also those where the second and so forth arguments are defaulted.

The MathLib::TemplateVector3 is an exception, because of the many
required changes through the code, which relies on the implicit
conversion from TemplatePoint<T, 3> to TemplateVector3<T>.

clang-tidy '*explicit*' check.

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.

Especially on iterator types and 'new' allocations.

This is automatic replacement with
ag '(?<!std::)size_t(?!\w)' --ignore-dir=ThirdParty -l | xargs perl -pi.bak -e  's/(?<!std::)size_t(?!\w)/std::size_t/g'

New protected init().

integrated new mesh-classes into gui, rewrote some methods because everything is much shorter and easier now; some fem-related files and adaptions are still missing