OmniPresence support in OmniFileExchange and lots more.

General:
- The frameworks have only been tested on Mac OS X 10.8.3 and iOS 6.1. We have not yet set the deployment target to 10.8, but will in the near future.
- Worked around cases of the ARC writeback misfeature <http://llvm.org/bugs/show_bug.cgi?id=15649>
  - Lots more explicit '__autoreleases' scattered around to make things build with our '-fobjc-arc-disable-writeback' patch

A few highlights:

Configurations:
- Better support for static library framework-like targets on Mac OS X

OmniBase:
- Added some convenience methods for logging errors and suppressing logging thereof (for unit tests expecting errors)

OmniFoundation:
- Switch to using SecTrust exception data in OFCredential support for certificate trust checks
  - On the Mac, it is expected that you'll use the system provided certificate sheet to make permanent changes
- Added OFLockFile.
- ARC-ify a few more files
- Fixed thread-unsafety in parsing ICS/ISO-8601 dates due to use of thread-unsafe CF API
- Coalesce updates to OFNetStateRegistations to avoid complaining from mDNSResponder
- Added NSFileCoordinator helper wrappers

OmniFileExchange:
- Added document syncing support used in OmniPresence and our iPad apps.
- Added regression tests for document syncing

OmniFileStore:
- Add support for turning off transfers on cellular networks
- Disabled ETag support in DAV conformance testing. No DAV server we've found actually conforms to WebDAV, and ETags are ill defined, so we stopped using them.
- Handle multistatus responses from MOVE/COPY
- Added a notion of a 'Trash' document scope on iOS. Deleted files get moved there.
  - On the Mac, deleted files get moved into the user's normal trash.

OmniSoftwareUpdate:
- Avoid spinning up the discrete GPU
- Fixed zombie when installing updates in some cases

OmniAppKit:
- More faithfully reproduce the responder chain search for OATargetSelection
- Move Message of the Day support here from OmniSoftwareUpdate
- Much improved support for font matching in OAFontDescriptor. Added unit tests.

OmniUI:
- Document syncing support via OmniFileExchange

TextEditor:
- Cleaned up a few glitches in the sample app
Merge https://github.com/omnigroup/OmniGroup