[Refactor] Extract module OptionsHelp from Options

Put all help texts in one place.
[Refactor] Move methods from ConfigLoader to Config

Takes care of the code smell "Feature Envy" in ConfigLoader and
makes it smaller. Two birds with one stone.
Merge pull request #999 from jonas054/refactor_class_lengths

Refactor for smaller classes
Improve messages of lint cops
Merge pull request #1003 from yujinakayama/improve-lint-offense-messages

Improve messages of lint cops
Fix LineEndConcatenation to handle chained concats