Performance & memory improvements

[leonardehrenfried]

The bulk of the memory consumed by OTP is in the road network. We would like to decrease this number in order to fit larger areas (ie. the entirety of Germany) into a single machine.
Ideas to decrease memory usage:

• Use smaller data types: it seems that things are needlessly stored in integers what should be byte or short
• bicycleSafetyValue is a float when it could be a short
• traversalPermission is a reference (potentially 4 bytes) when it could of type byte
• streetClass is an int when it could be a byte
• Use bitsets to store all road properties
• Outgoing edge lists in the index are ArrayLists of capacity 10, when often they contain far fewer items
• Vertex labels contain the OSM vertex id as a string. Calculate it on the fly rather than storing it

Other ideas to improve are very welcome.