Revision 1887020

Review EscherContainerRecord#getChildRecords() call sites for unnecessary work

This started off as wanting to add the EscherContainerRecord#getChildCount() function in order to do an efficient check for how many children the container has. This was desirable in new code for editing HSSF pictures. The existing option of calling getChildRecords().size() was undesirable as this requires a list copy first.

In the process of finding call sites that would benefit from replacing getChildRecords().size(), I realized that several other patterns would benefit from eliminating a copy, such as iterating over the children in a for-each loop, and indexed access to specific children.