Check for block creation after submitblock

* Initial commit to resolve issue #21
* Changed submitblock to check for the block's existance
* Should stop false positive block accepts
* Updated names in lib/template_registry.py ro reflect scrypt vs sha256 hash
* Changed the number of argmuents that submitblock takes. Ensure it is called with all 3 arguments if making changes.
* See issue #21 for the details surrounding this commit/change set.
* *May* introduce a race condition if theblock is not created before we check for it.
* Front end should generate scrypt hash and locate it from the database due to potential false negatives.