Make onto_extract and check_urls less developer specific.

[grosscol]

Currently, the ruby and bash scripts make assumptions about the locations of artifacts on disk that are inherent in my system. As such, they won't run on another's system.

These scripts need to be independent of the idiosyncrasies of a single developer's file system.

• Handle caching ontologies on disk.
• Handle reading from cached copy or fetching from remote.
• Handle invoking script from via symlink
• Handle invoking script from directory other than project root.