Pyfomod

* Fixed TypeError when passing strings to *path* argument of `Installer`.

* Added installer shortcut to `Root`.
* Warnings have been reworked into subclasses and moved to a new module, `warnings`.

* Improved parser reliability on broken syntax:
* Invalid attributes that resolve to enums now use the default value;
* Missing required attributes are to a sensible default;
* Some missing required attributes are REALLY required (like file paths) so they are just skipped;
* All of the above will produce a proper warning.

* Fix Installer error when request file/flag list.

* Fix validation callbacks' return value handling - they are now being properly treated as a list.

* First stable release.
* Added installer support.