AbstractTransformer: allow empty companion class names for local interfaces #1625
CeylonVisitor: we don't always need a companion class builder #1625
ClassDefinitionBuilder: removed checks for the need for companion parts since we will skip the entire companion if needed #1625
ClassTransformer: only generate companion classes when required #1625
Renamed LocalInterfaceVisitor to InterfaceVisitor and make it check if we need companion classes too #1625
model loader: keep track of whether model-loaded interfaces have/need a companion class #1625
Test for #1625: remove companion classes when not required
Updated tests .src for #1625: remove companion classes if not required