Change Markdown to XEP-393 styling

[mimi89999]

No description provided.

[hantu85]

Siskin IM (as well as Beagle IM) has support for Markdown and we are not willing to remove it. We could add XEP-0393 styling as a separate style that could be selected by the user (instead of Markdown) but as this pull request intentionally removes Markdown support (even without renaming files and functions) and converts it in XEP-0393, it cannot be accepted.

[mimi89999]

I think that Markdown support shouldn't be kept because most clients (like Conversations, Dino, etc.) support only XEP-0393 and it will be bad if styling is not consistent across clients.

As for renaming files, I agree that they should be renamed and I can do that.

[hantu85]

And I think it should stay, as people (generally speaking, not just XMPP users) are more familiar with Markdown than with XEP-0393.

Also

Markdown support shouldn't be kept because most clients (like Conversations, Dino, etc.) support only XEP-0393

is not a reason to remove Markdown support but, at most, to add support for XEP-0393 without removal of XEP-0393.

In XMPP it is a freedom to choose which XEPs to support and which not to support. At this point, we do not support XEP-0393 but we do support Markdown.

As for XEP-0393, (as I've already mentioned on XMPP Summit when it was discussed), I think that an issue with this XEP is that it allows usage of XEP-0393 markup without marking stanza (or <body/> element) that text is actually styled and does not indicate what styling is used.