g.E() creates too many Operations

[p29876]

Describe the bug
g.E() should map to a single Gaffer OperationChain.
Instead it creates 2n + 1 queries, where n is the number of edges in the graph.

(1) GetAllElements
     For each edge found:
        (2) GetElements(src)
        (3) GetElements(dest)

This is causing unacceptable performance for simple queries