PostTyper transformers

1) reorders companion objects so that they allways follow matching
classes
2) removes imports and named arguments
3) rewrites all trees holding types are to TypeTrees
TreeTransform: add support for transforming stats

Added a prepareForStats&transformStats pair of methods,
which provide a convinient way to alter scopes of
PackageDefs, Templates and Block's.
CreateCompanionObjects transformer

A transformer that provides a convenient way to create
companion objects.