Default eContents for EObject subclasses is not efficient

[gdaniel]

It is implemented using a containment list, and the get(idx) iterates all elements before idx, creating many unnecessary database calls.

[gdaniel]

Partially solved for get() method

[yvrng]

Solved in #69 : All EMF Iterators and Collections have been reimplemented, using batch methods (such as #getAll, #addAll) to avoid atomic calls to the database.