Unify node and edge list creation in one script

In an effort to make this script more modular I am restructuring it
into phases.

The first phase reads the ULAN XML into a hash, including all the
associative_relationships. The second phase writes the data out into
the desired format - in this case, CSV files. A node list is created by
iterating through the hash, then an edge list is created in the same
way.
Merge xpath query with iteration

This means we don't have to create another variable that is just
immediately ready and then unused after.
Improve comment clarity and spacing
Place several puts status messages

Notify user when parsing and reading XML has begun, and when writing
the node and edge lists has begun.
Clarified line spacing
Script deprecated, already combined into id_name_table.rb
Clarify subject_ID variable name
Read subject description, and create weblink to Getty
Merge branch 'dev_unify'