Stop using GryoMessageSerializer

[FlorianHockmann]

TinkerPop will remove the GryoMessageSerializers completely in version 3.6.0: TINKERPOP-2639 and instead recommends to use GraphBinary. Due to the breaking change in serialization of Geoshapes via GraphBinary coming in #2876, I suggest that we only use GraphBinary by default in a version that already contains that change, so probably 1.0.0.

We could also switch to GraphSON instead if we want to move away from Gryo earlier, but it's probably fine to just directly move to GraphBinary in 1.0.0. So, I'm adding this to the v1.0.0 milestone for now.