Allow time mutation around initial end time only

[jfbischoff]

Depending on the source of the demand generation, time mutation of agents should be limited to optionally mutate around the initial end times only. I.e., an agent with an activity end time at 8:00 and a mutation range of 18000 seconds should always start their activity between 7:30 and 8:30.

[davibicudo]

activityParams compatible/dependent with/on initial plan times would also be nice to have at some point :)
e.g. so that the agent isn't deadlocked in a penalty situation, being forced to arrive always too late at work.