1) completed shift to Markdown and appearance fixed (thx @lastivka); 2) new tags introduced; 3) rev. 32 released; changelog:
* markdown is now displayed correctly
* `<phr>` tag removed as it was already present in <ex>
* `<abr_def>` tag: attribute `type` introduced
* `<xdxf>` has new obligatory attribute: the `revision` (version) of the format standard the file adheres to
* visual format is now considered as not recommended
* `<file_ver>`, `<creation_date>` were made obligatory meta-info
* examples now adhere to the format specs (thanks to @lastivka)
* `<categ>` tag introduced
* `<ex>` tag `type` attribute might have value `oth` now; `mrkd` tag introduced; attributes `source` and `author` introduced
* `<kref>` tag: `kcmt` attribute introduced
* `<def>` tag: `id` attribute is case-sensitive (as in HTML)