Introduce StorageService#readAll()

When loading a large project model from a database many individual
requests were created, which can be quite time consuming.

This patch introduces a new method readAll() following a consumer
pattern that allows loading a complete model at once. The JPA
implementation uses a CursorStream to read the database in chunks,
thus considerably lowering the number of requests fired against
the backend.

Change-Id: I89613ff4e1315a43b9d8a9c1ad25a32527308c5e
Signed-off-by: Michael Ochmann <michael.ochmann@sap.com>
5 files changed