T_cycle is unnecessary redundant parameter

[sbenthall]

T_cycle is given as a parameter to AgentType.
But the software breaks if this is anything but the length of time-varying parameters, which elsewhere is collected directly.
It can be removed from the parameters list and replaced with an automated calculation in the constructor.

Though this is also a case where possibility of a 'cycle' being a 'lifecycle' i.e. cycles == 1, or a non-cyclic model, is confusing terminology.