We no longer need the custom counterpart. The things that were
changed in it and reasosn we no lomger need them are:
1. set separator - this can be done with standard counterpart
2. ES6 port: this was done to allow importing as _t, but is
unnecessary with the _t wrapper function in react-sdk
(although also seems to work fine with
`import _t from 'counterpart';`)
3. Fallback to key name: unnecessary with
`setMissingEntryGenerator` in 0.18, but we've changed to just
using a fallback locale anyway since No code missing en
translations should ever make it to the devbelop branch.
4. Logging on missing translations. Unnecessary with
`onTranslationNotFound`, but now not used anyway because we
let missing translations show up in the UI as
'missing translation'
Bulk changes to imports coming in separate commit for easy reading.