RTF import: handle right-to-left tables

Change-Id: If2e60557b7551839c344d56cb3a720ae3659e93c
oox: these are expected to be UTF-8

Change-Id: I2e9cb96948d7f990dd8be5f4505f00306fa62f8f
TabDialog ctor: take an OUString

Change-Id: Ie390fb9debe3a80b3ebc5e609119723c78eadba2
drawinglayer: these are expected to be UTF-8

Change-Id: Ic2054af851bb9d195be4d550f36b1d7349f90204
vcl: let the Dialog ctor take an OUString

To make the conversion in the TabDialog ctor unnecessary. Put
conversions to other subclasses till they are properly adapted.

Change-Id: I6152b6229ce9c840262739cf11812538c9e0a532