Add one test case to verify the dev_mode option for a release and
another to verify overriding the dev_mode option in a profile for a
release. Verification of proper dev_mode functioning is done in the
rebar_test_utils:check_results/2 function by checking if all the
directories in the release lib dir are symlinks or not and comparing
that result to the dev_mode expectation passed as input to
the check_results function.