[NEXUS-7657] Make rawcontent use ComponentStore

https://issues.sonatype.org/browse/NEXUS-7657

This gets rid of the direct orientdb/blobstore stuff and goes against the new ComponentStore.

Implementation note: With this change, AssetAdapters and ComponentAdapters are still registered automatically via sisu Mediators, but the storage classes are created lazily so we can be sure the requisite DatabaseInstance is initialized. However, note that we can't create them *too* late, because if a transaction is open against orient, it is not possible to make schema changes. So they are created by the new ComponentStore interface method, prepareStorage, so that components that need them to exist can request that they're created when the component initializes.  See RawBinaryStoreImpl.on(NexusInitializedEvent) for example. Together, this ensures that the underlying storage classes are created at just the right time, if needed. Making this a bit cleaner should be possible after NEXUS-7303 (support for @PostConstruct and @PreDestroy) is implemented.
Definitely an oversimplified example. I expect as we get into other more realistic views, we will see lots of examples of format-specific properties (and have more realistic use cases against which to judge the "fit" here). For maven, for example, GAV coordinates would fit in here if they need to be accessible/queryable as distinct fields. 

As currently implemented, there's a modeling exercise that needs to happen for any given format as we get into it. Which properties to add to the base properties is going to depend on the kind of component we're talking about, and what properties are considered interesting (and most importantly, which should be searchable) for it.

We *could* say, put a Map<String, String> or even JSONString in the base storage class if we wanted, and just have people shove whatever they want into there. But the place where I think having format-specific extensions of the storage classes is really important is when we want to index on specific fields per format.