Switched Tests to use .-based accessors

Switched InchCoordProxyTests and InchLocationTests from using getter and setter methods to the dot-notation setters and getters.  The “#pragma clang diagnostic ignore” lines that were recently added to each model's P001ModelSurrogate category make this possible without any warnings or errors.

Note: This turns the mistake that we've been calling setters on surrogates for a while now (which are by nature readonly) into a hard error.  Which is good, but bad. YKWIM

Minor:
• Moved object sets in InchLocationTests#testXYSurrogation to inside the brackets, matching InchCoordProxyTests's format.
• Switched `P001ModelSurrogate<…ish>` syntax to now-preferred `id<…ish>`
Replaced P001ModelSurrogate's @dynamic decls with #pragma

Replaced P001ModelSurrogate's @dynamic declarations for invalid and unset with a `#pragma clang diagnostic ignored "-Wobjc-protocol-property-synthesis"` @implementation prefix.