add formula read support
Created originally on Bitbucket by ericgazoni (Eric Gazoni)
we already can write formulas, but not yet read them back, so when reading a file with formulas, then writing it back, the formulas are gone
Created originally on Bitbucket by ericgazoni (Eric Gazoni)
we already can write formulas, but not yet read them back, so when reading a file with formulas, then writing it back, the formulas are gone