Core: added config check to disable URL to video embed transformations. This was prompted by a need within the Signatures plugin.
Core: added another condition to linkify/embedify method.
Merge pull request #1921 from vanilla/feature/config-disable-embeds

Core: added config check to disable URL to video embed transformations. This was prompted by a need within the Signatures plugin.
Merge branch 'master' of github.com:vanilla/vanilla into hotfix/profilextendcheckbox