Lib/Pluck created, officially deprecated Re::pluck

There were just too many issues with Re::pluck() and it's variants.

Most of these issues stem from the fact that Set::extract() is flaky with XPath syntax...
Though attractive and somewhat less verbose, it's not effective at handling arrays with mixed keys and a few other oddities.

Also, the Re::pluck() functions were a bit wonky on how they would "unwrap" results... they would do a `current()` for most result sets, but not all... was somewhat hard to predict what you'd get.

So....

I re-implemented most of the "use cases" for these methods in a new class:

* Pluck::one()
* Pluck::oneEmpties()
* Pluck::firstPathOrDefault()
* Pluck::firstPath()
* Pluck::all()
* Pluck::allEmpty()

These seem much more reliable.

NOTE:  you can not do a simple find/replace as the new methods are not drop-in replacements and no longer use the XPath syntax for pathing... instead they use the `{n}.User.id` or just `User.id` paths.

More on Paths:
http://book.cakephp.org/2.0/en/core-utility-libraries/hash.html#hash-path-syntax

Upgrade Recommendation:
* find all unique instances, uses of `/Re::pluck.*\(.+\)/`
* determine suitable replacement fo each simple one
* replace each globally
* find all stragglers and deal with them independantly