Use modern API for setting bundle bit when available.
Replaced OBASSERTSTRING macro with a thrown exception

* Saves having to import the definition for a macro
* Reverting without checking for the thread is a programmer
  error, and they should be slapped with an exception.
Make the class run with or without ARC

A bit messy, but a start.
Line up the #if #endif consistently
Remove the version guard around the replacement for deprecated functions

The replacement NSURL method:

    - setResourceValue:forKey:error:

is marked as available from 10.6, which is the base version that this needs
to work with - per Mike Abdullah.
Use coordinator instead of PSC as a local variable name
Revert "Remove the version guard around the replacement for deprecated functions"

This reverts commit fee631612814b20b4239aaeef97e981a20ebd5ab.
comment why the #ifdef so future generations aren't confused too.
Modern non-ARC compilation understands strong, so just use that.
restore comment
Consolidate setter memory management.
Looks like I actually had a potential leak in the old code :(
Throw a NSInternalInconsistencyException using convenience method.
Whoops, forgot to bail out upon additional content failure.
might as well do the retain slightly later
Simplify additional content cleanup.
might as well do the retain slightly later
In fact there's no need to retain _additionalContent during a synchronous save.
Don't actually need custom file manager.
Whoops, forgot to bail out upon additional content failure.
Replaced OBASSERTSTRING macro with a thrown exception

* Saves having to import the definition for a macro
* Reverting without checking for the thread is a programmer
  error, and they should be slapped with an exception.