Refactored IDocumentStylePoolAccess out of SwDoc.

Added non const SwDoc::GetDfltTxtFmtColl and SwDoc::GetTxtFmtColls
and SwDoc::GetCharFmts.
Had to make the manager friend of SwTxtFmtColl and SwConditionTxtFmtColl
Had to make SwDoc::_MakeCharFmt and SwDoc::_MakeFrmFmt public.

Change-Id: I19a36d91f92b3781a6c4313ec12eb8f7d4dfacc3