Merge branch 'develop' of https://github.com/stan-dev/stan into develop
moved tests for raise exception to no-main
test raise exception in model block
adding tests for model block behaviors
Merge branch 'develop' of https://github.com/stan-dev/stan into develop
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
add multi_gp_cholesky syntax tests
add function signatures tests for Frechet distribution
removed extraneous doublevectorview in pareto distr
add lomax_log with tests
switched lomax to pareto_type_2 and added rest of prob functions
added function signatures with tests
removed lomax
add pareto_type_2 to manual