Added option to select the module to reload routes of, refs #1878.

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | ---
| Fixed tickets | ---
| Refs tickets  | #1878
| License       | MIT
| Doc PR        | ---
It probably makes sense to assign `$repository = $this->entityManager->getRepository('ZikulaRoutesModule:RouteEntity')` for readability as you call it three times here.