Scour

* Fix [Bug 427309](https://bugs.launchpad.net/scour/+bug/427309) by updated Scour inkscape extension file to include yocto_css.py
* Fix [Bug 435689](https://bugs.launchpad.net/scour/+bug/435689) by properly preserving whitespace in XML serialization
* Fix [Bug 436569](https://bugs.launchpad.net/scour/+bug/436569) by getting `xlink:href` prefix correct with invalid SVG

* Fix [Bug 368716](https://bugs.launchpad.net/scour/+bug/368716) by implementing a really tiny CSS parser to find out if any style element have rules referencing gradients, filters, etc
* Remove unused attributes from parent elements
* Fix a bug with polygon/polyline point parsing if there was whitespace at the end

* Fix XML serialization bug: `xmlns:XXX` prefixes not preserved when not in default namespace
* Fix XML serialization bug: remapping to default namespace was not actually removing the old prefix
* Move common attributes to ancestor elements
* Fix [Bug 412754](https://bugs.launchpad.net/scour/+bug/401628): Elliptical arc commands must have comma/whitespace separating the coordinates
* Scour lengths for svg x,y,width,height,*opacity,stroke-width,stroke-miterlimit

* Remove attributes of gradients if they contain default values
* Reduce bezier/quadratic (c/q) segments to their shorthand equivalents (s/t)
* Move to a custom XML serialization such that `id`/`xml:id` is printed first (Thanks to Richard Hutch for the suggestion)
* Added `--indent` option to specify indentation type (default='space', other options: 'none', 'tab')

* Only convert to RRGGBB format if the color name will actually be shorter
* Remove duplicate gradients
* Remove empty q,a path segments
* Scour polyline coordinates just like path/polygon
* Scour lengths from most attributes
* Remove redundant SVG namespace declarations and prefixes

* Fix [Bug 401628](https://bugs.launchpad.net/scour/+bug/401628): Keep namespace declarations when using `--keep-editor-data` (Thanks YoNoSoyTu!)
* Remove trailing zeros after decimal places for all path coordinates
* Use scientific notation in path coordinates if that representation is shorter
* Scour polygon coordinates just like path coordinates
* Add XML prolog to scour output to ensure valid XML, added `--strip-xml-prolog` option