Switched to a 10.8 deployment target on Mac OS X

General:
	- Removed a bunch of code for old operating systems
	- Marked several places that still need attention with `#pragma clang diagnostic ignored "-Wdeprecated-declarations"`

OmniFoundation:
	- Added -isFileInTrashAtURL:
	- Removed -stringByReplacingAllOccurrencesOfString:withString: -- NSString has -stringByReplacingOccurrencesOfString:withString:

OmniAppKit:
	- Added -[NSEvent isUserCancel]

OmniNetworking:
	- Fixed bundle extension of ONUnitTests so Xcode would run them

OmniSoftwareUpdate:
	- Removed reporting of the "loc" key (user's general location set via System Preferences). ReadLocation() is deprecated and getting the user's general location isn't worth asking for location entitlements.

OmniUI:
	- Added -viewInAppStore: