Revert "Revert "[Azoth] Return unescaped contents from GetBody().""

This reverts commit fbdd44de615bea48d9cc747c20f683a3bf6030b8.

Well, SetBody(GetBody()) should be invariant after all.

Conflicts:
	src/plugins/azoth/plugins/mucommands/commands.cpp
[Azoth] CoreMessage now implements IRichTextMessage.
[Azoth] Support creating core messages with rich text.
[Azoth] Added DummyMsgManager::GetIMessages().
[Azoth MuC] Autoprepare standard contents from rich ones.
[Azoth] Show dummy messages on theme reload.
Merge branch 'unescape'