added a suffix other than weight to the quantity label

This is useful if you want to say "2 in cart" or something similar.
header for qty suffix.  also removed now used methods.
fixed some drawing issues with highlighted state of +/- buttons

Also fixed display of right image.
changes to make the class more customizable

including loading from a xib and not overwriting some of a user's settings in buttons
added a method to take the currentQuantity as the new originalValue

This is useful when changing quantity and the UI needs to reflect that the new state has been committed.
gave subclasses readonly access to the quantityBehavior and a way to customize the committing animation
call updateButtonState when setting a new baseline to make sure it stays in sync
Merge branch 'refs/heads/master' into productDetailsQuantityEditor
Merge pull request #2 from walmartlabs-asdaios/productDetailsQuantityEditor

Made changes to make SDQuantityEditView more customizable