Import foxglove schemas repo

This has to do a couple of things:
* Actually import the repo as an http_archive.
* Modify the cc_static_flatbuffer rule to allow it to handle a
  flatbuffer target with multiple fbs files.
* Move foxglove-related third_party files into one directory.

Change-Id: I0123fc8037b107019f9c29b781418c9a03639eca
Signed-off-by: James Kuszmaul <jabukuszmaul@gmail.com>
diff --git a/aos/flatbuffers.bzl b/aos/flatbuffers.bzl
index 3db4ca0..c26906a 100644
--- a/aos/flatbuffers.bzl
+++ b/aos/flatbuffers.bzl
@@ -1,16 +1,18 @@
-def cc_static_flatbuffer(name, target, function, visibility = None):
+def cc_static_flatbuffer(name, target, function, bfbs_name = None, visibility = None):
     """Creates a cc_library which encodes a file as a Span.
 
     args:
       target, The file to encode.
       function, The inline function, with full namespaces, to create.
+      bfbs_name, For flatbuffer targets that have multiple fbs files, this
+         specifies the basename of the bfbs file to generate a schema for.
     """
     native.genrule(
         name = name + "_gen",
         tools = ["@org_frc971//aos:flatbuffers_static"],
         srcs = [target],
         outs = [name + ".h"],
-        cmd = "$(location @org_frc971//aos:flatbuffers_static) $(SRCS) $(OUTS) '" + function + "'",
+        cmd = "$(location @org_frc971//aos:flatbuffers_static) '$(SRCS)' $(OUTS) '" + function + "' " + (bfbs_name if bfbs_name else "-"),
     )
 
     native.cc_library(