Adds a visitor for svgio for visiting svg nodes and create something
useful from them.

Basic draw commands - a tree of draw commands (with sub-pixel
precision support) just to store a simple definition for drawing.

Adds a svg draw visitor and create draw commands from the svg
structure and expose the commands through UNO API.

Change-Id: I073e891a2cffdd76d4e3b838590e3a19c998e9bf
Reviewed-on: https://gerrit.libreoffice.org/68770
Tested-by: Jenkins
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>