binman: Plumb in support for bintools

Support collecting the available bintools needed by an image, by
scanning the entries in the image.

Also add a command-line interface to access the basic bintool features,
such as listing the bintools and fetching them if needed.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/ftest.py b/tools/binman/ftest.py
index ac6aabb..179326c 100644
--- a/tools/binman/ftest.py
+++ b/tools/binman/ftest.py
@@ -18,6 +18,7 @@
 import tempfile
 import unittest
 
+from binman import bintool
 from binman import cbfs_util
 from binman import cmdline
 from binman import control