Make use of new TypeIDs in xcube

[TonioF]

In xcube, a new TypeID class has been introduced along with new identifiers. In particular, there is now a separation between a dataset and a dataset that is also a cube.
In xcube-cci, we want to have two DataOpeners: One to open datasets and one to open cubes, each opener is associated with the respective type id.

[TonioF]

Instead of TypeIDs, now TypeSpecifiers are used. This was done with a number of interface changes to the store framework which need to be considered by the cci store.

[TonioF]

Please wait, I realize I need to include two more changes.

[TonioF]

Closed by #19 .