FORGE-917 Fixes to ensure that immutable classes are not scaffolded.

These changes are introduced outside MetaWidget since the context is not available to determine whether the inspected class is being scaffolded or not. Hence, the decision to avoid scaffolding the class is taken well before inspection.
Merge pull request #324 from VineetReynolds/FORGE-917

FORGE-917 Fixes to ensure that immutable classes are not scaffolded.