svg: group transforms now pass the W3C SVG test suite

The initial attempt to translate matrix.x0 and matrix.y0 to
simple group offset was flawed. Now the given matrix is kept
as given and the groups position etc. are calculated with it.
The group' objects real coordinates are only moved without
a matrix, otherwise it's just a simple matrix change.

Also fix some comments/typos.
svg: support the full set of named colors

First simple implementation with bsearch(), if it turns out
to be slow while profiling it could be easily be converted
to a static leaked hash table.
[transform] Affine transformation for every renderer

DiaTransformRenderer is a renderer facade which adds basic transformation
support to every renderer. It implements the basic renderer interface to
translate the object given coordinates through the currently active
transformation matrix (given by DiaRenderer::draw_object()) and calls
the output renderer (worker) given at construction time.
Text and image transformation are still incomplete, but the rest should
be working fine.
Some transformation have to be done on the basic shape level, e.g. a
rectangle is turned into polygon; transformed ellipse and arc are rendered
as bezier path with some helper functions extracted from DiaPathRenderer.
svg: set fill-rule also for polygon rendering
svg: fix interpretation of units inch and pica
svg: add svgz to extensions for svg-import