Update os_boot.erb

Using the underscore character "_" for the separator can be problematic - if the <%= repo_url %> value contains an underscore .

My example, the repo was named "ubuntu_server" and of course the sed command would work out when hitting the underscore in the url (http://192.168.1.5:8080/svc/repo/ubuntu_server)

I replaced the delimiter with the character that has the octal value 001 - in ASCII it's the SOH character (start of heading) - which is extremely unlikely to appear in the repo name.

I think it is safer to use this.
Template and task revamp

The goal with this is to make the paths for finding tasks and templates more straightforward. This is done by removing os_version, adding ".task" to task folder, using "metadata.yaml" as a taskname convention, and allowing "/" and preventing "$" in task names.
Fixes https://tickets.puppetlabs.com/browse/RAZOR-154