Rework how we bypass browser caches of the scouting app

This patch adds a new way to access files on the webserver. Users can
now request files by their sha256 checksum. The URL pattern follows
`/sha256/<checksum>/<path>`. The `<path>` portion doesn't actually
matter, but it helps with readability.

This patch migrates the main bundle and the pictures to use the new
checksum-addressable scheme.

Signed-off-by: Philipp Schrader <philipp.schrader@gmail.com>
Change-Id: I76eaa9b0f69af98e48e8e73e32c82ce2916fbe41
diff --git a/scouting/webserver/static/test_pages/index.html b/scouting/webserver/static/test_pages/index.html
new file mode 100644
index 0000000..d769db4
--- /dev/null
+++ b/scouting/webserver/static/test_pages/index.html
@@ -0,0 +1 @@
+<h1>This is the index</h1>