It allows to define a multiline space-indented code block that will be properly parsed by the reST converter for the online docs.
The in-editor help understand the [codeblock] tag as it supposedly understand [code] already (i.e. it just seems to discard it, though the code was supposed to switch it to a monospace font, but that's likely another issue.
Fixes a number of issues:
- Headings underliners now have the correct length
- Newline+Tabs in descriptions are replaced by two newlines to make a proper paragraph
- [br] are replaced by two newlines, making a proper paragraph
- Properly parse internal hyperlinks in constants description
- Fix broken internal links due to missing newlines
- Show method header even when it has no description, to have something to reference in hyperlinks
