Fix of #56 - newModuleSymbol & newCompleteModuleSymbol

Needs new TypeRef creation method that works for NoPrefix and at the same time
does not need a denotation. This is provided by method TermRef.withNakedSymbol.
Fix for #55

Distringuish between ModifierFlags -- which can appear in trees -- and SourceModifierFlags -- which are
modifiers according to the language spec.
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.
Merge pull request #64 from DarkDimius/PostTyperTransformer

Post typer transformer