Shows picture of the day on login screen

Downloads picture of the day at any resolution we choose. Code in-place for future filters for image. Caches it and re-uses it - only one download per day max.
Fixed picture of the day resolution issue

The pic of the day thumbnail now is requested so it matches the screen height if it's a wide image or the screen's width if it's a tall image. Looks much nicer! Also refactored a bit adding code which can extract image metadata.
Fixed url encoding issue
Added pan recognizer to image of the day

Properly detects which way the image of the day can pan given that either its width or height is going to match the device's.
Removed pan recognizer
Pull image from Commons instead of English Wikipedia
Async image of day retrieval. Better caching. Faster json data access.
PictureOfTheDay object now relays image metadata to its "done" callback

Did this so the attribution button (also added) for the Image of the Day can reveal who contributed the photo.
Added @2x logo for retina display devices
First pass at hooking up Image of the Day attribution button
Merge branch 'featuredImage' into mergeAttempt

Conflicts:
	Commons-iOS.xcodeproj/project.pbxproj
	Commons-iOS/LoginViewController.h
	Commons-iOS/LoginViewController.m
	Commons-iOS/ThumbFetcher.h
	Commons-iOS/en.lproj/MainStoryboard.storyboard
Cleaned some post-merge cruft.
First pass at hooking up Image of the Day attribution button
Made PictureOfTheDay's getAtSize: method use "title"

Per Brion's comments.
Made attribution slide in and out. Tap to dismiss.
Picture of Day attribution text updates during the transition

Previously you'd have to hide and re-show the attribution to see the updated text.
Pictures of the Day saved in own directory.

Previously they were in the thumbs directory.
Refactored PictureOfTheDay object interface

Now it's easier to call it in different ways. Previously it would have been hard to call on a timer to cycle through a list of images. Now it should be easy.
Picture of the day cycles between all cached pics of the day

Also normalized bundling of a default pic of the day. To bundle a different default image just remove the existing cache file from the bundle (the presently bundled cache file is named "POTD-2013-05-24" - note that the cache file contains more than just the image - it contains attribution data as well) and bundle a different one and change the BUNDLED_PIC_OF_DAY_DATE define to reflect the date of the newly bundled file. Cached filescan be grabbed from the app's "potd" folder - and just change the PIC_OF_THE_DAY_TO_DOWNLOAD_DAYS_AGO define to force it to download and create a cache file for a particular image if you want a new one to bundle.
Didn't cycle pic of the day if download failed. Fixed.