remove public convenience methods that let the user avoid creating a CellAddress...

remove public convenience methods that let the user avoid creating a CellAddress object. Having the user provide a CellAddress increases the chance the user-provided object will be reused if possible. This also moves the validation of the CellAddress object outside of this BorderPropertyTemplate class (easier to debug), improves readability, and runs slightly faster since the CellAddress is needed anyways as a key.

git-svn-id: https://svn.apache.org/repos/asf/poi/branches/ss_border_property_template@1748065 13f79535-47bb-0310-9956-ffa450edef68