commit 2cb7d3c1
revealed DifOptions is always set to DifOptions::Excel,
so DifParser.bPlain is never true.

remove import with plain number formatter and DifOptions enum

Change-Id: I8e214f3fff8ecfc7e03622dd1fe3fb53c2fb1e25
Reviewed-on: https://gerrit.libreoffice.org/27277Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>