Added configuration permutations test from file to D2
Added the unit test D2CfgMgrTest.configPermutations to d2_cfg_mgr_unittests.cc. This test iterates through the list of test configurations defined in a specialzed JSON data file. It provides a relatively painless way to test a large number configurations without hard-coding them. Added the test data file: It currently contains over sixty tests. The vast majority of these tests are invalid content tests.