Config restructure to new format

[triwahyuu]

Type of changes

Please check the type of change your PR introduces: - [ ] Bugfix - [x] Feature - [ ] Code style update (formatting, renaming) - [x] Refactoring (no functional changes, no api changes) - [ ] Build related changes - [x] Documentation content changes - [ ] Other (please describe): ## What is the current behavior?

• close #7

What is the new behavior?

• new config format as described in #7
• deprecation check for old config
• None string value in config automatically converted to python None

Checklist

• [x] Unit tests pass locally with my changes
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] I have added necessary documentation (if appropriate)
• [x] Any dependent changes have been merged and published in downstream modules
• [x] I have filled the [Unreleased] Changelog

[triwahyuu]

ready for review, but documentation still not finished cc @alphinside

[alphinside]

lgtm