CPCollectionView Implemented - (CPView)draggingViewForItemsAtIndexes:(CPIndexSet)indexes withEvent:(CPEvent)event offset:(CGPoint)dragImageOffset
and the corresponding delegate method from where you can ask for the default dragged view. Multiple selection not implemented yet.
Merge remote-tracking branch 'upstream/master' into CPCollectionView-dragged-view
CPCollectionView dragging: fix a bug where the dragging view was created from content instead of selection
CPCollectionView : Allow the prototype view to be loaded from a cib

With this commit CPCollectionView can load subviews from an external
cib. Outlets, actions and bindings between the view and the
prototype are restaured when the view is loaded.
CPCollectionView test. Nib test and bindings test.

Bindings:
collectionView CPContentBinding -> arrayController.selectedObjects
prototypeView CPValueBinding -> owner.representedObject
Update min/maxItemSize lazylly instead of subclassing -awakeFromCib

Binders can set values before -awakeFromCib. We were too late
and the bound content was not visible.
Partially rewrote layout.

it is not optimal but certainly better than the previous  version. A
collection view was unusable when resized through its scroll view.
Freeze autoresizingMask

The mask is 0 and cannot be changed.
Cocoa allows any value but ignores them for layout.
-setItemPrototype:
    Do not cache removed items in -reloadContent when the item prototype changes.

maxItemSize:
    Interpreted as horiz/vertic expandable when zero size and the proto view has a CPViewWidth|HeightSizable. (per cocoa but not documented).
    maxItemSize height support.

Fixed: incorrect position when num items < numberOfColumns.

Rewrote layout engine. Splitted the computation of size, columns count, rows count from the actual layout where we set the frame.
This will help when/if we support insertion/mutation of  -content or view animations.
We can also be more lazy when the computation results stay the same.

Added shared -init. Whitespace cleaning.

CPCollectionviewCibTest:
    Add ability to set the 2 kinds of prototypes, one loading its view from a cib, the other with a view outlet in the same cib.
    Loaded protoype: the bound textfield can commit its value to the model.
    UI for setting maxNumberOfColumns|Rows min|maxItemSize
test app: CPSelectionIndexesBinding test
Merge branch 'CPCollectionView-dragged-view' into CPCollectionView-dragAndDrop
Simplify the "layout computing" method and change its name

There is not need to use that much arguments because the result is stored in ivars.
CPCollectionViewItem -copy: set properties correctly even if the collectionView overrides them.
Drop support with drop indicator.

FIXED: undefined _horizontalMargin
Test app: UI for switching uniformSubviewsResizing.
Merge remote-tracking branch 'upstream/master' into CPCollectionViewItem-loading
nib2cibed example
Merge pull request #1700 from cacaodev/CPCollectionViewItem-loading

CPCollectionView -maxItemSize support, content binding, collection view item loading ... [+4]
Refs #1700. Clean up and use macros.
Refs #1700. Make `reloadContentCachingRemovedItems:` a private method.
Refs #1700. Use more macros.
Refs #1700. Fix unknown class or global warnings.