Consider translation of transformation matrix of image rotation

Hi Armin, hi all,

this is about https://bugs.documentfoundation.org/show_bug.cgi?id=115590 
and my proposal https://gerrit.libreoffice.org/#/c/50176/

It works in principle, but I'm not sure about some details:

A
It has a construction
    basegfx::B2DHomMatrix aFullTransform;

    with later on
    if ( !aFullTransform.isIdentity() )

Should I use
    basegfx::B2DHomMatrix aFullTransform;
    bool bHasTransformation;

    if ( bHasTransformation )
instead?

B
It has
    if ( aTransformedCenterPosition != aCenterPosition )
Is this check useful, or should I calculate the correction always, 
although the result might be the original value?

C
Is this the correct place at all to correct the position?

Kind regards
Regina