Integrate logog library for logging

Logog is integrated into OGS and can be found in Base/logog. For a short introduction see the quickstart page.

See commit e4ab507b for a commented usage example.

On release builds the log level is LOGOG_LEVEL_INFO, on debug it is LOGOG_LEVEL_DEBUG and it can be overriden with the CMake option OGS_LOG_LEVEL. See also commit e0f58fb1.

@TomFischer and @rinkk: Please give a 👍 and I will merge it into master.

Logog was integrated as a git-subtree and can be updated with (executed in the sources root):

git-subtree pull -P Base/logog --squash https://github.com/johnwbyrd/logog.git

It was initially integrated with:

git-subtree add -P Base/logog --squash https://github.com/johnwbyrd/logog.git master