SES-1876 initial setup for moving DESCRIBE evaluation details into
EvaluationStrategy.
SES-1876 some initial setup for a DescribeOperator, incomplete.
SES-1876 bnode-closing implementation of describe operator implemented.
SES-1876 added javadoc
SES-1876 fix to account for the special case of the start value not
having any outgoing links.
Merged in ses-1876 (pull request #179)

SES-1876 implementation of bnode closure for DESCRIBE queries