We want to avoid the phenomenon where right after typing the first
character into a Writer documnent in a LibreOffice instance, spell and
grammar checking stuff is initialised which can take a quite long
time, especially the LightProof one.

Even after my recent change that made the Lightproof initialisation
clearly faster (by avoiding the import of the large
lightproof_impl_pt_BR.py module before actually doing Brazilian
Portuguese proofreading), there still was a 0.3 second delay on my
relatively fast machine.

This change moves that delay into Writer start instead, before any
document window is ready to accept input. At least then the user is
not entering text and wondering why it doesn't show up right away.

Change-Id: Ie578c310dc9cb9bfc964e2986eec177fb1d4e666
Reviewed-on: https://gerrit.libreoffice.org/56473
Tested-by: Jenkins
Reviewed-by: Tor Lillqvist <tml@collabora.com>