Use fast serialization lib for the graph

[abyrd]

Java stock serialization is very slow. Other libraries exist that should be much faster.

[buma]

Added to wiki

[abyrd]

Update: fast serialization uses stock Java serialization unless you write custom serializers. Marko has been trying this out. Since this is still in the experimental/evaluation stage, I'm moving this ticket to the current sprint.

[buma]

Tested this on current master and New York. It doesn't improve size and/or speed any more.

[abyrd]

Clarification: it used to help but apparently now that the graph objects are more compact (including geometries), these serialization libraries don't make much difference anymore.