Time and related classes were considered unneeded.

These classes and partial order of events made the model of a tour too precise.
Such models were considered to be both hard to code and hard to use.
That's why events made to be ordered externally (using list instead of set).
The event layout class was renamed.

This was done because it was considered that layout notion is applicable
not only to an event in a tour but to some state in time.
Some layout representation and invariant were added.
Couple of apply operations were implemented using the current implementation state.