Add option to append CSS styling to code block

[Hector Palacios]

The idea is to have a new parameter style=<string> that appends <string> to the style parameter of the 'syntaxplugin' div. This will allow for some CSS customization, like having two code blocks that you can compare side-by-side, by just adding style="float:left; width=50%":

{code:title=0x05 variant|style="float:left; width=50%"}

but also other styling, like border, background...