MATSim Code

updated changelog with recent changes.

code cleanup, and trying to reduce memory consumption by only storing those tags that are actually required later.

reduce memory usage by reusing Sets for allowed modes on links: Instead of each link having it's own set (typically most of them with identical entries), have a cache which stores and returns exactly one Set for a given combination of set-entries. In tests with differently sized networks, memory savings of about 25% for each network could be observed.