Set `config_dir` and `log4j` attrs. in attributes file

So, I decided to move them back since I realised that it’s nice to
manipulate the log4j configuration before actually including the
default recipe. To get around the issue with setting the log file for
an appender I decided to use `lazy` values (either through the use of
`lazy` or by creating a lambda/proc), which I think turned out to be
a quite nice solution, and another benefit of keeping the attributes
in the attributes file is that all defaults (or at least close to all)
are defined in the same place.
Make `jvm_performance_opts` default more readable