refactor(vkApi): remove obsolete legacy things

Completely remove things like `XFR`, `XFR2`, `vk_ext_api` etc.
Replace `vkMD5` function with `md5-jkmyers` module.

This closes #135.
refactor(vk_lib): remove obsolete `remixmid` function

`remixmid` essentially returns `window.vk.id` now.
It was needed back in times when vk.com wasn't fully ajax,
and some pages hadn't `window.vk`.

Remove `remixmid` function, replace its calls with `window.vk.id`.

This closes #136.
refactor(inject): don't inject `_ext_ldr_vkopt_loader = true`

Remove obsolete legacy `_ext_ldr_vkopt_loader` flag.

This closes #139.
refactor(audio): don't call `sorter.update()` in `vkAudioShowOnlySize()`

Previously audio size text was not `absolute`-positioned,
but static (ordinary positioning), so it could easily change audio element
height. It was necessary to update markup. See also #28.

But now it's just pointless.

Remove `sorter.update()` call from `vkAudioShowOnlySize` function.

This closes #138.
feat(i18n): change "users_dislike" en translations

Use "X persons dislike this" instead of "X users disliked it".

This closes #127.