.pytool/Plugin: Add a plugin LicenseCheck

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2691
REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2833
Add a plugin to check license conflict for new added
files in a patch. It will report out errors when meeting
files which are not contributed under BSD-2-Clause-Patent.

Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Signed-off-by: Shenglei Zhang <shenglei.zhang@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

.pytool/Plugin/LicenseCheck/LicenseCheck_plug_in.yaml

@@ -0,0 +1,11 @@
+## @file
+# CiBuildPlugin used to check license issues for new added files
+#
+# Copyright (c) 2020, Intel Corporation. All rights reserved.
+# SPDX-License-Identifier: BSD-2-Clause-Patent
+##
+{
+  "scope": "cibuild",
+  "name": "License Check Test",
+  "module": "LicenseCheck"
+}