make imagine and slideshow classes configurable like the rest

fix service definition files to use parameters for class names


| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | yes
| Deprecations? | no
| Tests pass?   |see travis
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

The BC break is normalizing the parameter names for slideshow and imagine block and admins to have the persistence.phpcr prefix. this affects slideshow_admin, slideshow_document, imagine_admin and imagine_document.