Make all compilers support shortcodes

[ralsina]

It's a small change on each of:

• [x] orgmode
• [x] asciidoc
• [x] bbcode
• [x] commonmark
• [x] kramdown
• [x] markmin
• [x] mediawiki
• [x] misaka
• [x] mistune
• [x] odt
• [ ] rest_html5
• [x] textile
• [x] txt2tags
• [x] wiki
• [x] ~~wordpress_compiler~~

I have not checked if any of them already do.

[ralsina]

Maybe @felixfontein can do it for wordpress_compiler? It looks complicated and I don't want to break it :-)

[ralsina]

rest_html5 needs some refactoring to match latest rest plugin

[ralsina]

For the wiki compiler, I just added a note that it's not supported.

[ralsina]

Keeping it open for the last few plugins.

[felixfontein]

Hmm, I'm kind of skeptical to add shortcode support to the WordPress compiler for two reasons:

1. it already has support for WordPress shortcodes (like [gallery] and [code]...[/code]), so having a second similar syntax with different (!) shortcodes is kind of confusing; also, adding support for both types requires decisions on how to correctly parse posts which contain both kind of shortcodes;
2. the main purpose for the compiler is to translate imported existing blog posts. Therefore, I do not want the compiler to recognize a syntax which WordPess doesn't support, and which might be contained in some existing blog posts which suddenly are translated differently.

So if there's ever support for Nikola shortcodes in WordPress posts, there should at least be a global configuration flag which allows to disable this (I'd even tend to enable that flag by default, i.e. you must explicitly enable Nikola shortcodes).