updates to be able to do block-wise Gibbs
bugfixes and easier to read code
put in correct exception type
-added method to compute log_likelihood of current state under different interface
-fixed dimension problems
implenmented missing abstract methods and fixed bugs in conditionals
added log_lik evaluation for Gibbs samplers and fixed some mini issues
added method for solving linear systems with precomputed cholesky
initial working version of Gibbs sampler
working test for gaussian gibbs