Removed trailing white spaces

Removed trailing whitespaces with

```sh
for file in `grep -r " $" * | cut -d : -f 1 | sort | uniq | grep -v " "`; do sed -i 's/[ \t]*$//' $file; done
```

and some handwork.

templates/mail/notify/collaborator.tmpl

@@ -10,7 +10,7 @@
     <p>
         ---
         <br>
-        View it on Gogs: 
+        View it on Gogs:
         <br>
         <a href="{{.AppUrl}}{{.RepoLink}}">{{.AppUrl}}{{.RepoLink}}</a>
     </p>