Redirect opensocial APIs to graasp APIs

[vohtaski]

java/graaasp/src/main/java/org/apache/shindig/graaasp/jpa/spi/SpaceServiceDb.java

implements the logic which is similar to Graasp

Instead of implementing things twice, we should redirect all calls to opensocial API into Graasp. Shindig will remain a widget renderer proxying calls to Graasp when needed.

Why?

1. Remove database from shindig (make it lighter and more maintainable)
2. No double implementation of features (owners of space, hidden spaces, etc.)
3. Future-proof: easier to add new features in Graasp, or migrate to new Graspio (mongodb database and not mysql)

[vohtaski]

@voz I added few whys? If I missed something, could you please add

[vohtaski]

related:
#16
#5
#20

[vohtaski]

#16 is related to ILS (database problem), folder spaces don't have a parent in shindig implementation