Refactored IDocumentContentOperations out of SwDoc.

Into the new class DocumentContentOperationsManager.

Made SwNodes in sw/inc/ndarr.hxx friend class to
DocumentContentOperationsManager so it can call DelNodes at end of
DocumentContentOperationsManager::DeleteSection .

Added DeleteAutoCorrExceptWord to SwDoc, its needed in the Manager.

Added a non const version of SwDoc::GetDfltGrfFmtColl() to SwDoc
because its needed in the Manager.

Made SwDoc a friend class to DocumentContentOperationsManager so it
can call SwDoc::checkRedlining and SwDocL::_MakeFlySection.

Moved SwDoc::CopyImpl_ , SwDoc::CopyWithFlyInFly and
SwDoc::CopyFlyInFlyImpl into the Manager.

Moved "struct ParaRstFmt" and "lcl_RstTxtAttr" from docfmt.cxx
in DocumentContentOperationsManager.hxx .

Change-Id: Icaab57f4a8c158a85e549ecb4aacc752bc95bbc9