The Sparse' module parts are used also if unsupported
module support is turned off.

 - formatting
 - system includes vs. project includes
 - use absolute paths

Closes #3100.

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

VecGetArray function requires the accessed vector not
to be locked.

add gmres restart test1

set gmres restart test2

add restart option for all Preconditioners (final)

Saves ca. 35 unneeded includes (out of 260)
and 25s of compilation time (out of 149s).

No INFO/ERR/WARN/DBUG calls in this files.

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...

operator() (IndexType row, IndexType col)

Mostly in the file headers.

find *Lib -type f | xargs sed -i 'N;s%^\s\+\*\n\(\s\+\*/\)%\1%'

Fixes multiple copyright messages in the doxygen docu.

ag '\\file' -L --ignore=ThirdParty *Lib |xargs  sed -i 's/\(.*\)\\copyright/\1\\file\n\1\\copyright/'