Provide version info at runtime

The version is retrieved from package metadata in production.
For development the version is taken from git.

The version string strives to be compatible with PEP-440

NC-44
Include version into web UI of DRF

NC-44
Add version function for the API call

nc-44
Add docs for retrieving version of NC

nc-44
Merge branch 'develop' into feature/nc-44-2
Merge branch 'feature/nc-44-2' into 'develop'

Provide NC version both via API and DRF UI, NC-44

Dmitri, please pay attention to the way version obtaining code is implemented, namely 450c8476e commit.

The rest of commits are cherry-picked from your and Ilja's work.