IVGCVSW-6779 Add build-tool Docs and update docs

* Added Arm NN Build Tool README.md and license.
* Added Dockerfile diagram image and license.
* Updated existing guides: added note to the cross
  compile guide to use build-tool, removed content
  from the Delegate BuildGuideNative.md.
* Added Arm NN logo image to homepage README.md
  and added license.

Signed-off-by: James Conroy <james.conroy@arm.com>
Change-Id: I9306ad24165cf3b0203c2a1852ec3afd718e9eab
diff --git a/Arm_NN_horizontal_blue.png.license b/Arm_NN_horizontal_blue.png.license
new file mode 100644
index 0000000..db7c467
--- /dev/null
+++ b/Arm_NN_horizontal_blue.png.license
@@ -0,0 +1,4 @@
+#
+# Copyright © 2022 Arm Ltd and Contributors. All rights reserved.
+# SPDX-License-Identifier: MIT
+#