The GraphUtilities static functions should always create a new core

We do this as GraphUtilties methods are always used for specific
isolated tasks such as parsing and/or analyzing a block of DS code
Merge pull request #113 from junmendoza/StableBranch_FixGraphUtilitiesBehavior

Fix graph utilities behavior
Merge pull request #111 from ambarish-prakash/LocalStable

Refactoring of Parse function used by CBN
Error for import and language blocks in CBN