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
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
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.
Merge branch 'develop' into feature/issue-427
reordered terms in term grammar to fix issue #239
Merge branch 'feature/issue_394' of https://github.com/stan-dev/stan into feature/issue_394
test file from Bob
fixed failing test
updated make help message
added spaces
added spaces
Merge branch 'develop' into feature/issue-427
Add unit test for refresh=0 and refresh>0