Generalization of InchCoordProxy to ObjectSurrogate

Throughout the implementation of InchCoordProxy, I've been hit over and over with the idea that most of this is non-specific any particular class, that it should be easily generalized to any work with any conforming class.  Likewise, I've been hit with the idea that `Proxy` is too vague of a term for this concept, and that terms like `Trampoline`s are used in the Obj-C community.

I finally settled on a dynamic class name of `ObjectSurrogate`, from Objective-C Runtime Programming Guide's Message Forwarding chapter's Surrogate Objects section, which defines it as such:

> Forwarding not only mimics multiple inheritance, it also makes it possible to develop lightweight objects that represent or “cover” more substantial objects. The surrogate stands in for the other object and funnels messages to it.

That sounds like it fits.

So here's what happened:
• InchCoordProxy became ObjectSurrogate, and `InchCoord` by name all over became just `Instance` and `InchCoord` by type became `NSObject`.
	• Added a surrogateWithInstance: convenience constructor.
• InchCoord-specific properties moved to an `InchCoordish` protocol, which both `InchCoord` and a new `ObjectSurrogate (InchCoord)` adhere to.
	• Likewise, InchLocation-specific properties moved to an `InchLocationish` protocol, with `InchLocation` and a new `ObjectSurrogate (InchLoacion)` adhering.
•  @dynamic declarations for InchCoord and InchLocation properties now in the respective `ObjectSurrogate (…)` categories.
• InchLocation now returns `id<InchCoordish>` objects for `x` and `y`, rather than literal `InchCoord *`s _(since they'll likely be `ObjectSurrogate`s most or all of the time)_.
	• Getter implementations replaced with ones that create autoreleased ObjectSurrogates.
• In InchLocation.h, `@class InchCoord;` forward declaration replaced with `#import "InchCoord.h"` (`@protocal InchCoordish` was initially tried).
	» _I don't even want to tell you how many weird errors the compiler pukes when it is told to follow a protocol but doesn't even know if the `id`-typed instance is an NSObject or an NSProxy.  Except I'm not sure if that was the culprit.  It just was fuked._
• InchLocation posts an `InstanceWillDie` notification (of the `InchCoordWillDie` fame) in its dealloc.
• New P_001InchLocationTests, which currently have one test, `testXYSurrogation`— which tests values and persistence of InchLocation's x and y properties, much like `testProxyPropertyPersistence`.
• P_001InchCoordProxyTests updated: `InchCoordProxy` to `ObjectSurrogate<InchCoordish>` mostly, and a few other change-overs.
WIP P001Model