Set frontpage module to static frontpage if it is deactivated, closes #104

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | --
| Fixed tickets | #104, #760
| License       | MIT
| Doc PR        | --

I did not test upgrading from 1.3.5 to 1.3.6. I only tested upgrading the SettingsModule from *before* this PR to *after* this PR.