In case of no match by foreign-keys, we search by edge-type. This can happen if the type (edge owner)
is named T, but the edge-schema E names its edge field as u_id. We consider it as a match if
there is only one usage of T in E.
Thus, calling AddE with the same edge values, ignore and not throw an error.
For edge-schemas with extra fields, we maintain the same logic because we cannot
determine if the extra fields have different values that what exist in the database
Also, added additional example where an edge schema has another edge
to a type that holds an information about the relationship.
The only reason this example exists is to allow users to reduce the storage
occupied by the join-table and allow connect (via M2O) multiple edge-schemas
to an 'information'/'description' node.
