Fine grained File interfaces

[codeliner]

The File interface raises some questions. Its methods imply that we are dealing with a class or interface file, but what about config files or files that only contain functions?

My suggestion is to use dedicated interfaces that extend each other:

• File: very basic, maybe only contains the generate method
• PhpFile extends File: adds namespace, imports and injectVisitors methods
• ClassLikeFile extends PhpFile: adds all class/interface related methods

Does it make sense for this library to support non-PHP files? Or should those be handled outside of php-code-ast?