Reimplementation of SQL-backed Blueprints API implementation.

So far only H2 is tested (by the virtue of the passing
Blueprints testsuite).
Support for properly configuring the datasource
from the provided configuration.
Update the README.
Usability: be able to use the id given in any number class.
README updates
Edge should not have the hashCode/equals based on
id but rather on the other defining criteria.
Merge pull request #1 from metlos/master

Query support + general rewrite (almost)