scour.py, scour.inkscape.py, scour.inx:
* Add options --quiet, --enable-comment-stripping, --shorten-ids, --remove-metadata, --renderer-workaround.
scour.py:
* Optimisations in time (so Scour runs faster) and space (so Scour allocates less memory, less often).
* Change #E+# to #e#, #E-# to #e-#, 0.# to .# and -0.# into -.# in path/polygon/polyline data + lengths, if renderer workarounds are disabled. Use spaces instead of commas in path/polygon/polyline data. Use lower-case #rrggbb and #rgb instead of upper-case. All of this makes gzip work better, since the rest of SVG documents mostly has lower-case letters in tag names and spaces to separate XML attributes etc.
* Fix a bug whereby an SVG document would become filled with black if all elements had the same fill color.
* Fix a bug whereby a path's second command would not start at the right coordinates if the first command was a relative moveto 'm' with at least 1 implied lineto.
* Fix a bug whereby a path's absolute lineto 'L' commands would not become the right relative lineto 'l' commands.
* Allow the implicit linetos after a path's moveto 'M'/'m' to be converted into relative horizontal linetos 'h' and vertical 'v' too.
scour.inx:
* Fix help typos. Make options more descriptive in the plugin option window. Add something about enable-group-collapsing requiring enable-id-stripping.
testscour.py:
* Rework tests that relied on #E+#, #E-#, 0.# and -0.# so that they accept the changes to scour.py. Add unit tests for strip-xml-prolog, enable-comment-stripping and remove-metadata.
