implement orcus::spreadsheet::iface::import_table interface

Just some stubs to check that it is working.

Change-Id: I24e61cd24030ca5adeb07222fd63464d836ecb3d
make these types future proof

Our core already supports more than 32k sheets and we should not use
sal_Int16 anymore for sheets.

Change-Id: Ifeb321cba044b255ef2e7d34da0908c27877d6ae
use orcus for table import

This is a proof of concept and shows that it is possible to partially
replace the OOXML import with orcus.

Change-Id: I610cec4ba4ec6f966848397ec9f0c465520a3c65