add missing configureListFields method for imagineBlockAdmin

| Q                     | A
| -------------       | ---
| Bug fix?          |  yes
| New feature? | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | none
| License       | MIT


Hi, here is a small fix into imagineBlockAdmin where no field was displayed in imagine block lists

Thanks