Make a start on processing shapes on a sheet out of a record. For now, doesn't actual...

Make a start on processing shapes on a sheet out of a record. For now, doesn't actually manage to do this, but has much of the infrastructure that'll be needed. Includes ability to get an existing HSSFPatriarch for a sheet, if there are the required records, and for the HSSFPatriarch to be in a position to be given the shapes that make it up (but this isn't done yet)

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@610608 13f79535-47bb-0310-9956-ffa450edef68