Filled out methods of data augmentations class and most of population class, added outline for characteristic class
Initial complettion of characteristic class, continued working on Data Augementation class
Added log-posterior for measurements to DataAugmentation::InitialValue, other random changes
Continued work on population parameter, added getters and setters, moving lodens_pop to population parameter.
Moved log-densities of chi|theta to PopulationPar class.
Initial finish of PopulationPar class