Added are_expparam_dtypes_consistent to method to abstract class and reverted is_outcomes_constant to is_n_outcomes_constant.
Added are_expparam_dtypes_consistent to method to abstract class and reverted is_outcomes_constant to is_n_outcomes_constant.

QInfer/python-qinfer,whitewhim2718/python-qinfer,csferrie/python-qinfer,ihincks/python-qinfer,MichalKononenko/python-qinfer,Alan-Robertson/python-qinfer