Use UICollectionView rather than AQGridView
Update to iOS6 minimum version (as lower versions don't have UICollectionView).
Suggest https://github.com/steipete/PSTCollectionView/tree/master/PSTCollectionView if support for older versions is required.
Fix warnings 'created' by making iOS6 minimum version.
Padding is different using UICollectionView to AQGridView.
Fix update issue (where UICollectionView is not initialised when handleRefresh is finished)
Merge remote-tracking branch 'origin/master' into uicollectionview

Conflicts:
	BakerShelf/ShelfViewController.h
	BakerShelf/ShelfViewController.m
	BakerView/BakerViewController.m
Updated Version number and Build number to reflect the actual version of Baker
Change the gridView frame on rotation to mimic the display behaviour of AQGridView.
Merge pull request #918 from benoitchantre/master

iOS Application Target: version and build updated for 4.1
Merge pull request #818 from sdarlington/uicollectionview

Use UICollectionView rather than AQGridView
Added support for removing issues

When an issue is removed from shelf.json, a refresh will cause the corresponding issue to be removed from the Baker shelf.

Closes #957.
Added error message for unsuccessful unzip

The message may be displayed when the HPUB file is downloaded successfully, but something goes wrong when trying to unzip it.
Push status for refresh button is now visible

Fixes #947.