Merge branch 'develop' of https://github.com/stan-dev/stan into develop
Merge branch 'develop' of https://github.com/stan-dev/stan into develop
added raise_exception, compiles, tested by hand
added models for integration test
added tests for functions which throw exceptions
moved tests for raise exception to no-main
test raise exception in model block
switched order of error checks, made error messages more consistent, updated unit test
adding tests for model block behaviors
Merge branch 'develop' of https://github.com/stan-dev/stan into develop
cleanup - code for raise_exception stmts should be in branch issue-748, not in this one.
stan models that test error detection, error message
cleanup - wrong branch for these test models
fix multi_gp_log() signature in doc
sync multi_normal and multi_normal_cholesky

rearrange the code so that it is more evident which code parts
are shared and which are different between multi_normal and
multi_normal_cholesky distributions
use dedicated variable for Cholesky factor in tests

don't reuse Sigma variable to store its Cholesky factor
cleanup multi_gp

remove unused headers and 'using' directives,
update template parameter names
cosmetics for Weibull
add Frechet distribution

based on Weibull code
add multi_gp_cholesky distribution