Remove unused webcore import

This was causing a compilation failure when webcore could not be found.
Add failing tests for #SCL-4483
Fix #SCL-4483: allow implicit parameter list on getter for overloaded assignment

Moved duplicated no-arg check into the ScAssignStmt trait to
allow reuse in both ScAssignStmtImpl and AssignmentAnnotator.

Changed implementation to use parameter clauses to differentiate between
no-arg methods and parameterless methods while allowing a single
implicit parameter list.

Added tests to validate new behavior.
Merge pull request #31 from jgulotta/scl-4483

Fix SCL-4483