Cleanup import in segments.common:

- move `import re` to top
- if import is in a `try` block and there is some processing before it and
  `except` move this to `else`.
Merge branch 'common-imports' into develop
Fix non-ASCII directories processing

Fixes #788
Merge branch 'fix-788' into develop
Initial support for #770

What was done:
- Implemented loading using configuration hierarhy as proposed in the issue
- Implemented group aliasing

What was not:
- Some tests (config_reload) are failing
- Other (test_configuration) are spamming console with unexpected messages
- No support for powerline-lint
- No tests for new functionality
- Specifically I have not checked whether group aliasing actually works
- Colorschemes were not ported

Some other things: I have named this branch `config-ng` because I have other 
ideas about configuration and it would be good to include them making only one 
possibly backwards-incompatible merge commit instead of many. Specifically I am 
going to rebase `merge-config` branch here.
Move some color defintions to colorscheme/*.json
Update documentation