Dima/cleanup

[dorezyuk]

PR cleans up the code a little bit:

1. remove unused getError methods and the definition imported by it (I suppose this was used some time ago and left here)
2. remove the overwrite of resize, since g2o sets the all vertices already to 0. see
   https://github.com/RainerKuemmerle/g2o/blob/c64f79af4b7308a0505a05831f46e0dffb9a0c45/g2o/core/hyper_graph.cpp#L70
3. add a config-interface, so we can reuse it in all base-edge classes (reduces the copy and paste code)

[dorezyuk]

getter actually not required, so it could be dropped