Long read times for chunky schedule

[KasiaKoz]

Reading in a MATSim schedule of size ~1GB which relates to a non simplified network takes a long time (~5 h O_O)
Looking at memory usage, it looks like a long constant hang, probably when the underlying schedule graph is built. Methods about this may need to be revised.

[KasiaKoz]

Not able to read a 2.1 gig schedule.xml file - terminated process (AWS batch job) after 9 hours (I did check that it didn't run out of memory - I think it's just very slow standing up the underlying data structure of the Schedule object)