DATAKV-87 - Allow definition of target Map type via @EnableMapRepositories.

We added the configuration attribute `mapType` to `@EnableMapRepositories` which allows to change defaulting of the `Map` structure used by the `MapKeyValueAdapter`. To do so we now register a `MapKeyValueAdapterFactory` and delegate creation of the adapter to it. This also allows usage of interface types such as plain `java.util.Map` which will initialize the adapter with the approximable type resolved via `CollectionFactory`.