Add support for goog.module based imports

- option to enable goog modules
- golden file based tests
- based on moduleName for the current file

Based on @vojtajina's initial work.
The similar code is in `Compiler.compile()`.

I think a better fix would be to move the `moduleName` option processing from `Compiler.compile()` to `Compiler.transform()` (and no change here in `NodeCompiler`, we want to avoid changes in this derived class that are not node specific.) We could leave the optional argument `moduleName` on transform for back-compat but I'm ok with removing it also.