Fixed bug in ModuleExplorer.

passing the correct type of method to this.showEditorForFunction
Toggling is_ctor flag on CompiledFunctions
Implemented renaming class for ModuleExplorer.
Default superclass name is Object
s/get_class/get_core_class/ in Interpreter
Implemented CompiledModule.newClass and .removeClass
ModuleExplorer: adding and removing classes.
Checking for exceptions on startup.