Small fix for:
"PHP Notice:  Undefined index: singular_slug in app/src/Bolt/Config.php
on line 217"
Add ability to define attributes for image fields. Only 'title'
supported/required now.
Handle case where template designer uses <img src="/files/{{ record.image
}}">
Merge pull request #996 from GawainLynch/feature/ImageAttributes

Feature/image attributes
Merge pull request #992 from GawainLynch/hotfix/singular_slug

Small fix for PHP Notice: