UI: fix c++-mode for interfaces.idl
RSVG: docu fix
RSVG: remove unused functions
RSVG: provide Svg::BBox::to_string()
RSVG: remove deprecated g_type_init()
UI: exterminate ImageFrame, rename imagerenderer.{hh|cc}
UI: rename ImageRendererImpl
UI: move image rendering from ImageImpl to ImageRendererImpl
UI: imagerenderer.cc: stretch images
UI: add Image::element
UI: add LayerPainter
UI: move ImageBackend member from ImageRendererImpl to ImageImpl
UI: add StatePainter to display state dependent SVG image elements
RCORE: add outwards_index()
RSVG: add Span::distribute()
RCORE: TESTS: test Svg::Span::distribute
RSVG: add Svg::Element::stretch to h/v stretch and render an SVG element
UI: ImageRendererImpl::SvgBackend: lookup hscale/vscale spans for stretched SVG images
UI: ImageRendererImpl::SvgBackend: scale & render SVG images like pixel images
RSVG: Svg::Element::stretch(): properly support shrinking