ID import on keyed fields

[tgruben]

Description

Current keyed fields will not allow id imports. For performance reasons and the addition of the key-id enpoint , we should allow id imports into keyed fields given the assumption that the user is responsible pre-allocating the ids.

Success criteria (What criteria will consider this ticket closeable?)

import endpoint should work with ids into keyed fields

[yuce]

Java client implementation: FeatureBaseDB/java-pilosa#140

[yuce]

Go client implementation: FeatureBaseDB/go-pilosa#207