* Replaced all from ...py23 import * with explicit name imports, or removed completely when possible.
* Replaced tounicode() with tostr()
* Changed all BytesIO ans StringIO imports to from io import ..., replaced all UnicodeIO with StringIO.
* Replaced all unichr() with chr()
* Misc minor tweaks and fixes
Some SVG authoring tool write arc commands without any space or comma around the boolean 'large-arc' and 'sweep' flags, leading our svg path parser to choke.
This makes the path parser smarter by special-casing arc command parsing so that it only consumes one character ('0' or '1') for these special boolean flags.
