Consolidated configuration

Proposed changes to managing configuration files in storm-crawler.

A new ``conf`` directory has been added as a Maven resource. Topology config files, and other config files (such as ``urlfilters.json``) are placed here. When specifying a configuration file for running a ConfigurableTopology, the user has two options; (a) give the path of the config file on the filesystem, or (b) reference a config file in the ``conf`` directory by name.