Added '-warn' option to verify_sdp.sh to convert errors to warnings.
This option takes a list of named tests, using the same set of tests
names as used with the existing '-skip' option. Rather than skipping
the tests entirely, with '-warn' wany would-be errors are instead
reported as warnings. Warnings will not cause a non-zero exit
A new environment variable is added to go with the new option. Similar
to how the existing '-skip' option has a corresponding
VERIFY_SDP_SKIP_TEST_LIST setting the Instance Vars file, the -warn
option has a corresponding $VERIFY_SDP_WARN_TEST_LIST.