Move several JS files in the cpp module to imports.

All of these files are generically useful and not specific to C++.

- BundleTools/DarwinTools are useful on OS X in general and are used by
  both the C++ and Interface Builder modules.
  PathTools also uses DarwinTools.
- PathTools is currently only used by the C++ module but contains
  general filename functions that can be shared across multiple native
  language modules, like C++, Go, etc.
- WindowsUtils contains functions general to the Windows OS.

These imports should not yet be documented as further refactoring is
necessary.

Change-Id: I503773af268eabf8a77ebfc8a5809b9ddcad7af2
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>