Modified the ooxml_util_pkg.get_xlsx_column_ref and the
ooxml_util_pkg.get_xlsx_column_number functions to support columns up to
the limit (currently XFD or 16384) and in
ooxml_util_pkg.get_xlsx_column_ref to fix the bug where the '@' is
returned at multiples of 26.
Added a new function within the ooxml_util_pkg body that will return a collection of the worksheet records that include the name of the worksheet, the sheet ID of the worksheet, and the relationship ID for the worksheet. This will allow for the ability to look-up worksheets and parse them without needing to know what the worksheet's name is in advance.
Change XPath query to get all <t> nodes under the <si> node of interest,
regardless of their depth. This concatenates the resulting text() nodes
together.
