To change the appearance of the cursor, we use the CSS cursor style
and set the url to a data URI scheme. The image data sent via the
cursor pseudo-encoding has to be encoded to a CUR format file before
being used in the data URI.

During Canvas initialization we try and set a simple cursor to see if
the browser has support. Opera is missing support for data URI scheme
in cursor URLs.

Disabled for now until we have a better way of specifying settings
overall (too many settings for control bar now).