Redmine

The attached patch adds to the "#issue_id" from the email notifications a link to the issue page. This link is very useful when you read the emails on the phone or small screens and you want to quickly open the issue page.

Currently, you need to scroll down until the end of the email to find the line with the issue subject (h1 element). Also, some email clients (like Inbox from Google) hide that content after first reply because it find it duplicated. I have attached some examples:
- inbox.png which contains a screenshot with the notification received from #7360 in Inbox. You can observe that in the respective screen, there is no link to the issue.
- office.png which an example from office 365 popup. Here I need to scroll down to find the issue.

With the attached patch you can easily open the issue page:

If you consider that this change should contains a test, please let me know.

I've added the link also on issue_add.html.erb only for consistency.