* Migrate to `unittest2`
why:
Global symbol overflow when running NIM 1.2 on Github ci suggests that
unit tests run sort of separately. The replacement library `unittest2`
provides that.
* Build ci dependencies
* random helpers
* arrayops as a home for small array/openArray utilities
* assign2 - a replacement for genericAssign and assignment operators in
general which in nim are very slow
* use assign2 in a few places to speed things up
* fixes
* fixes
tersec
Jordan Hrycaj
Jacek Sieka