Retina, iCloud, and ARC updates

Some of the highlights...

General:
  - Now requires Xcode 4.3.
  - Started migrating towards ARC. Not all the way there yet.

OmniUI:
  - Removed unused images
  - Added @2x image variants
  - Added OUIEmptyPaddingInspectorSlice for pushing some slices to the bottom
    of an inspector
  - Added custom keyboard support to OUIInspectorTextWell
  - Replaced OUIAlertView with OUIAlert
  - Added some accessibility support; more to do
  - Finished conflict resolution UI and support
  - Finished iCloud configuration UI and migration of files
  - Finished support for notification of incoming deletes of open documents
  - Automatically close documents when reverting fails (due to the file
    being deleted while the app is in the background)
  - Fixed issues with preview generation while documents are being moved,
    deleted, updated (delay the writer block until we are done).
  - Added support for rendering previews of conflict versions
  - Added support for updating OUIDocument's references to attachments after
    being informed of a move by NSFilePresenter
  - Added Retina-awareness to preview generation
  - Added Retina-awareness to icon selection for import/export pane
  - Added support for badging files that are not on iCloud when iCloud is
    enabled
  - Improved the performance of opening/closing documents
  - Fixed a few edge cases of document renaming cancellation
  - Fixed parent view calcuation for OUIEditableFrame's controls.
  - Added support for locking interaction on the document, but letting
    alerts still have user interaction enabled
  - Don't open conflicted/not downloaded document on launch
  - Added top-level Omni Sync Server item to import/export

OmniFileStore:
  - Added support for migrating documents into/out of the ubiquity scope.
  - Added support for resolving conflicts.
  - Added support for automatically downloading small documents when on Wi-Fi
  - Reduce the number of redundant scan operations
  - Add support for informing the OFSFileStore delegate of move/copy
    operations (used to update preview cache w/o rebuilding them).
  - Properly deal with iCloud asking us to relinquishing to writer.
    This is complicated. Response to changes is buffered until we reacquire
    or processed immediately if we aren't in a writer block.
  - A bunch of other iCloud bug workarounds, and cleanup
  - Add file item support for tracking whether an instance is in iCloud and
    whether a download has been requested (even if it hasn't started).
  - Disable ubiquity support on iOS if the device is not running 5.1 or later

Configurations:
  - Code signing updates
  - Enable GCC_WARN_ABOUT_DEPRECATED_FUNCTIONS and
    CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS
  - Add notes next to a few other new warnings about why they aren't on yet

Scripts:
  - Run Xcode's pngcrush on iOS when copying library resources
  - OmniRunUnitTests handled more configurations
  - Added Scripts/rubylib/xcodeproj.rb, a simple helper for dealing with
    Xcode projects

OmniBase:
  - Added ARC helper macros, OB_STRONG, OB_BRIDGE, and OB_AUTORELEASING
  - Added OB_FOR_IN
  - Added OBASSERT_IF
  - Added some unit tests

OmniFoundation:
  - Turned off GC support, but not all the code is removed.
  - Made the public header ARC safe
  - Updated OFUTI to service more requests out of our local plist instead
    of trusting LaunchServices (which will return crazy info from other apps)
  - Made OFBindingPoint an object instead of a struct, for ARC
  - Made a few other classes ARC compatible
  - Add -[NSProcessInfo isSandboxed]

OmniAppKit:
  - Removed implementations of deprecated methods
  - Declare some used methods as API (moving towards enabling -Wselector)
  - Removed implementation of deprecated drag source method from
    OADragController and the delegate (no longer used).
  - Reeanbled OA_USE_COLOR_MANAGER for now. Still need to find a replacement.
  - Removed duplicate implementation of quarantine extensions
  - Remove NSTableView(OAExtensions) -tableView:draggingSourceOperationMaskForLocal:
    hack. Use the public API.

OmniQuartz
  - Added very basic performance logging for -renderInContext:.
  - Enable -[CALayer(OQExtensions) renderInContextIgnoringCache:] on iOS

TextEditor:
  - Removed the Midsummer.rtf sample for now. This sample app needs to be
    updated to avoid memory warnings/crashes when generating Retina scale
    previews for large documents