Allow to configure core_pattern and core_directory for the dea host

Sometimes, the vendor would like to configure the core_pattern and core_directory in some scenarios.
1. To customize the core_pattern, e.g. some runtime did not support %t option in the core pattern, since the warden shares the same core_pattern with the dea host. In case the runtime corrupted, the core dump file will not be generated successfully.
2. The vendor hope to use other tools to manage those generated core dump files, e.g. by default, in ubuntu, apport could be used for this purpose, so, while starting the dea/warden/file_server, it is better that different core_pattern value could be configured.