Rename dist -> distance and squared_dist -> squared_distance, enable squared_distance in the modelling language and readd the reference documentation.
Missed %
Fixed header guard issue.
Merge branch 'develop' into feature/add-dist-funcs

Conflicts:
	src/stan/agrad/matrix.hpp
fixes issue #464
added diag_post_multiply to signatures and tested compilability
added acknowledgement for bug report
updated command and base_hamiltonian to catch std::exception instead of std::domain_error to catch all Boost math and Stan throws, fixes #476
added tests for pre/post multiply, fixed bug in post multiply
added pre/post-multiply tests for agrad matrix rev
Move from using a char prefix to string prefix
removed default null character from mcmc_writer and replaced with empty string
fixed issue with mcmc_writer_test using char rather than string
Merge branch 'develop' into bugfix/issue-464-diag_pre_multiply
moving test files
Updated signature of test implementation to restore valid compilation
Merge branch 'develop' into feature/add-dist-funcs

Conflicts:
	src/stan/agrad/rev/matrix.hpp
	src/test/agrad/rev/matrix/squared_dist_test.cpp
	src/test/agrad/rev/matrix/squared_distance_test.cpp
	src/test/unit-agrad-rev/matrix/squared_dist_test.cpp
	src/test/unit/math/matrix/dist_test.cpp
	src/test/unit/math/matrix/squared_dist_test.cpp
Allow refresh=0 to silence all iteration output.
updating unit-agrad-fwd/matrix/diag_post_multiply test
Merge branch 'develop' of https://github.com/stan-dev/stan into develop