Only allow single parameters & blocks when signatures request "all" parameters
Fix exception error message
Correctly make URL loader's cache static
Make some util functions static
Revamp GlobalScope null handling

• GlobalScope's now return NOT_FOUND when the requested variable is not known; this allows globals to have null values without performance implications.
Engine class cleanup

• Make non-interface methods private
• Fix parameter names
Document public interface and classes
Fix javadoc links
Fix scm tag in pom
[maven-release-plugin] prepare release root-0.0.1