The IsAdmin flag is set based on whether the admin filter
returned any result. The admin filter is applied with the user dn
as the search root.

In the future, we should update IsAdmin as well on each login.
Alternately, we can have a periodic sync operation.

Conflicts:
	modules/setting/setting.go

Conflicts:
	templates/repo/release/list.tmpl
	templates/user/dashboard/dashboard.tmpl

Conflicts:
	routers/repo/setting.go

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.