is_same_v<> for is_same<>::value
decay_t<> for decay<>::type
is_integral_v<> for is_integral<>::value
invoke_result_t<> for invoke_result<>::type

TYPED_TEST_CASE is deprecated, please use TYPED_TEST_SUITE since googletest 1.10.x.

This are all but backward Euler.
The few testcases in H2-pp were updated to backward Euler
without loss of accuracy.

 - All processes using a Newton scheme are discretized
for the backward Euler scheme only. They are not usable
with other time discretizations.
 - Greatly simplifies code maintenance in this part.

NumLib tests are still not unity build.

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

Clang format run on near-the-header lines.

Happy New Year

See #1989.

Fixes warning: suggest explicit braces to avoid ambiguous ‘else’

to set a local vector of a processor from the global one.