This commit undoes some of previous commit in attempt to be less "hackish".
-When importing LibreOffice generated ODS documents, use cached formula
 results instead of always recalcuating.
-For other generators, do hard-recalc.

Still need to:
-Stop matrix formula cells from being set dirty to avoid recalculating them.
-Implement special cases for functions that should always be recalculated.

Change-Id: I959872aa2f446b80f9204ee26e94de7140f1f6f9