Retiring variations of using brackets as a denominator for footnotes

[markcheret]

There have been a load of support tickets opened because of how footnotes are being denominated, especially those using ((brackets)).
Is there a safe way to parse those?
Or should we think about

• phasing them out over the next few releases (with an option to auto-convert to another format)
• move the default setting for new installations to something like [fn]footnote[/fn]
• both?

[Rumperuu]

Currently, I think changing the default to something else would be a good short-term fix. [fn]/[/fn] is unlikely to clash with anything, but I do feel like part of the appeal of the Plugin is the simplicity of the ((/)), which is lost somewhat with that. That said, Easy Footnotes uses the relatively cumbersome [efn_note] and that doesn't seem to have done it any harm.

As we currently don't do any static parsing of posts, auto-conversion would be quite a bit of work to implement (but it may be able to piggyback off of a feature like #107 if/when we get around to implementing it). However, #121 should mitigate a lot of the ((/)) conflict issues because DOM parsing will solve things like the Plugin detecting footnotes inside <script> tags, etc.