Fix compile errs resuling when NOM_BUILD_JSON_UNIT is turned off
CMakeLists: Distribute default set of fonts with nomlib.framework

(This is from the feature/GUI branch, SHA 968d35b).
File: Introduce directory iteration methods

* File: Change IFile pointer type from shared_ptr to unique_ptr.
* UnixFile: Introduce is_dir, read_dir methods.
* WinFile: Implement exists, is_dir, read_dir methods.
types: Fix MSVCPP compile err