Added EntryURL variable to be available in email template

[cjhubbs]

Added a variable called EntryURL which can be used in an email template to link back to the original item in case a reader wants to visit the originating site.

[slurdge]

Thank you for the pull request. From my understanding, you want the same functionality as IncludeLink but when the Entry is not put in a digest and you hare directly the title ?
If that's the case, I would suggest the same approach, i.e. in run to have a test if IncludeLink filter is here and transform the Title to include the <a>....</a>

[slurdge]

I kept the default template as-is but users will be able to modify it.