Squashed 'lib/aihrus/' changes from 3cd7b93..cf897a7

cf897a7 Add abstract class Aihrus_Settings

git-subtree-dir: lib/aihrus
git-subtree-split: cf897a79e27bc2d0ee7ccf714904404d7564dfca
Merge commit 'cfb563da6b38b448956bfcf3d97da0bf7b5c49c6'