Un-clusterified InchCoord

As well-meaning as the work on creating an InchCoord cluster class was, I just don't think it's necessary at this point, and too much complexity at this level.  It did prove out some aspects of how P001Model should work, so it wasn't a complete waste.  And the “formula” that was figured out for it may become useful later.

• Combined InchCoord and InchCoord_double implementations into a double-native InchCoord, similar in code and functionally the same as what existed before the cluster conversion.
• Removed InchCoord_NSNumber implementation.
• Removed unnecessary comments, pragmas, and constructs for cluster class stuff.
Un-clusterified InchCoord

As well-meaning as the work on creating an InchCoord cluster class was, I just don't think it's necessary at this point, and too much complexity at this level.  It did prove out some aspects of how P001Model should work, so it wasn't a complete waste.  And the “formula” that was figured out for it may become useful later.

• Combined InchCoord and InchCoord_double implementations into a double-native InchCoord, similar in code and functionally the same as what existed before the cluster conversion.
• Removed InchCoord_NSNumber implementation.
• Removed unnecessary comments, pragmas, and constructs for cluster class stuff.
Merge branch 'feature/puck-dynamics' into 'adhoc/travis-build-test', forcing to the state of the former

Forced to the state of feature/puck-dynamics by:
1. Checking out 'feature/puck-dynamics' and running `git merge -s ours adhoc/travis-build-test`.
2. Checking out 'adhoc/travis-build-test' and hard-resetting to the new merge commit (currently, feature/puck-dynamics).
3. Checkout out 'feature/puck-dynamics' and hard-resetting to HEAD^ (feature/puck-dynamics commit prior to the merge).

The only downside to this approach is that on adhoc/travis-build-test, HEAD^ (HEAD^1) points to the feature/puck-dynamics commit, while HEAD^2 points to the prior adhoc/travis-build-test commit.  This is opposite of normal, and can be a little confusing when referencing HEAD^ (though adhoc/travis-build-test is named “adhoc” for a reason).
Merge branch 'adhoc/travis-build-test' into feature/unit-models
New GeoSpace model

• New GeoSpace model, which is just a singleton instance with no properties.
• New SpaceModelTests tests, with basic init and surrogate tests.
• Added GeoSpace.h/.m and SpaceModelTests.h/.m to the project file.
	» Added by hand, so there's a good chance it won't work when opened in Xcode.  And a slight chance that it will (though Xcode will probably renumber/reorder things.)
Merge branch 'adhoc/travis-build-test' into feature/unit-models
WIP: Uncommented coarse->fine assert within assertBothUpAndDownConversionRatiosCorrect
Merge branch 'adhoc/travis-build-test' into feature/unit-models
Fix (attempt) for GeoSpace dealloc crash

It appears that the crash that was happening with GeoSpace#dealloc within SpaceModelTests#testGeoSpaceInitialization was caused by the shared singleton instance being alloc/inited only once, but release/dealloced multiple times.

There are, of course, a few approaches to fix this.  Considered were doing an extra release with each init, leaving init as normal and documenting that the singleton must be accessed via a +shared… method (as per Cocoa), or hacking retain/release/autorelease/dealloc to not do as they're told.

The approach taken was to override retain, release, and autorelease to bypass normal functionality only if the instance is the sSharedGeoSpace instance, leaving dealloc as it normally is.  The idea is that normal usage (e.g. alloc/init, retain, autorelease, retain, release) will just use the sSharedGeoSpace instance and never move the retain count from 1, however, by bypassing the normal initialization (by using objc_msgSendSuper() to alloc a GeoSpace via its parent class's alloc and calling initIgnoringSingleton), one will have a normal instance and everything will work as it should.

Also:
• initSharedGeoSpace was renamed to initIgnoringSingleton in order to reflect more closely what it does, rather than the common use-case.
Merge branch 'adhoc/travis-build-test' into feature/unit-models
Merge branch 'adhoc/travis-build-test' into HEAD
Merge branch 'adhoc/travis-build-test' into feature/unit-models
Added invalid and unset tests to testGeoSpaceInitialization

SpaceModelTests's testGeoSpaceInitialization previously only tested that after alloc/init, the instance was non-nil.  It also makes sense to test the invalid and unset states of the object, since they're universal to all P001Models.
Merge branch 'adhoc/travis-build-test' into feature/unit-models
Merge branch 'adhoc/travis-build-test' into feature/unit-models
Merge branch 'adhoc/travis-build-test' into feature/unit-models
Created ScreenSpace model

• Created ScreenSpace; it's (currently) a clone of GeoSpace (since both are placeholders for general, singlular concepts).
• Added ScreenSpace to the project file, by hand.
• Added tests in SpaceModelTests matching GeoSpace's for ScreenSpace.

Also:
• In GeoSpace, renamed sSharedGeoSpace to sSharedInstance since the general concept is more important internally than the type and there's no possibility of conflict.
	• Likewise in ScreenSpace.
Merge branch 'adhoc/travis-build-test' into feature/unit-models
Consistified GeoSpace and RealWorldUSLengthUnit naming to Reality–

The choice to renamed from a Geo– or RealWorld— prefix was made because the former sounds planet-based (like latitude and longitude) and the latter is clumsy.  Also, Reality– is a stronger reference to the AR concepts this'll be used for.

• Renamed GeoSpace to RealitySpace in model code, model filename, tests, and project file.
• Renamed RealWorldUSLengthUnit to RealityLengthUnit in model code, model filename, tests, and project file.
	» Notably, This is RealWorldUSLengthUnit moving away from its US Imperial Unit System-specifc focus to a more general unit focus in one class.  Meters and such should be added later.
Merge branch 'adhoc/travis-build-test' into feature/unit-models