Mobile theme removed, closes #1046, #1336

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    |  mobile theme does not exist anymore
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #1046, #1336
| Refs tickets  | -
| License       | MIT
| Doc PR        | -