Make absolute template paths work.

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | ---
| Fixed tickets | #627
| Refs tickets  | https://github.com/zikula-modules/Content/issues/135, #1685
| License       | MIT
| Doc PR        | ---