[#70] lazy-load metadata instances

- Instead of pre-loading `Metadata` instances, create them only when
  they are retrieved. Change is 100% BC with previous version.
Updated QA tools

- Removed php-cs-fixer
- Added phpcs
Fixed CS errors/warnings flagged by phpcs
Merge branch 'hotfix/70'

Close #70
Merge branch 'master' into pr66-im-bart