Update of config_tool.cpp which creates the tool realm_config.
Update of config_tool.cpp which creates the tool realm_config.

The code has been cleaned up a bit internally and there are two changes
in the output.

The first change is when realm_config is called with no arguments.

realm-config

The old version had no output. The new version outputs the help message.

The second change is the output from

realm-config --version

The old version had the git version as output. The new version takes its
output from realm/version.hpp.

realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core