Add support for generating SVG with inline option enabled

[mojavelinux]

The HTML-based converters support embedding the SVG directly into the output document. This happens if the inline option is set on the image node (i.e., opts=inline). This extension should make it possible for a user to set this option on image nodes when the format is SVG.

One idea would be to expand the acceptable values of the mathematical-format attribute to include svg-inline. The extension would split this into the SVG format and the inline option.

[ProgramFan]

This sounds great.