Finished up the add, add unique and remove methods for object arrays as well as full coverage unit tests.
Added the ability to PFObject to save a list of PFObjects using the three saveAll methods.

Closes out Issue #2.
Extended the PFObject class to support three static deleteAll methods.

Closes out Issue #3.
Removed the virtual declaration from some PFObject protected methods which should not have had it.
Added support to PFObject for fetchAll and fetchAllIfNeeded.

Completes Issue #4.