Moved all the help files to markdown files:

Files moved:
* Workflow
* help/ssh
* help/webhooks
* help/system_hooks
* help/public_access
* help/permissions
JSON Lint the web-hooks.md file

Thanks to @jojosch for the initial work on the web-hooks.html.haml file!
Merge pull request #6308 from jvanbaarsen/help-to-markdown

Convert all help files to markdown files in doc directory