RLDT:
* Exploration can be turned on and off on the fly: the exploration bonus is always determined during value iteration but only added (when choosing action) in the case of exploration being turned on.
* Added function to delete models
* Trees can be updated for experience lists
* Bug fix: train only specified model (i.e., reward, state variables)

IRLDT:
* Estimate mu:
  * turn off exploration when estimating mu
  * only count mu when terminal action reached.
* Bug fixes