refactored loading of elements from persistent as it was just too inefficient previously
fixed testing bug where it was pointing to a real local db
added commit and rollback to AmberDb
corrected table name (edges -> edge)
updated transactional graph and unit test.
merged the latest changes from master branch.
Merge pull request #25 from nla/amber-sql

Amber sql merged.
updates to cmdLoad and cmdExport.