Add the new test suite.

This test suite has been in use for a long time now, in place of the obsolete and unmanageable testparser.py and testfuncs.py. It verifies the complete optimizer output to stdout and stderr, to ensure that the output matches the expectations.

See unit_tests/README.txt for more info.

unit_tests/expr.suite/experience-emsg.out

@@ -0,0 +1,34 @@
+[ "unknown error id"
+, "unknown error id"
+, "no error"
+, "exceeded throttle"
+, "experiences are disabled"
+, "invalid parameters"
+, "operation not permitted"
+, "script not associated with an experience"
+, "not found"
+, "invalid experience"
+, "experience is disabled"
+, "experience is suspended"
+, "unknown error"
+, "experience data quota exceeded"
+, "key-value store is disabled"
+, "key-value store communication failed"
+, "key doesn't exist"
+, "retry update"
+, "experience content rating too high"
+, "not allowed to run in current location"
+, "experience permissions request timed out"
+, "unknown error id"
+, "unknown error id"
+, "unknown error id"
+, "unknown error id"
+, "unknown error id"
+, "unknown error id"
+, "unknown error id"
+, "unknown error id"
+, "unknown error id"
+, "unknown error id"
+, "unknown error id"
+, "unknown error id"
+]