Removing icon_type column

Icon type is not used consistently. It is used initially
during the loader. Afterwards, we save both the icon and resource to the db.
Instead of changing the logic to always read the shortcut-resource first, and fallback to the bitmap if the resource is not available,
always write the bitmap to DB whenever the shortcut is edited.

Change-Id: I0ea5e88f8904bd3250ca669220b3e5d6aeef1bfd