[cdc_stream] Add a CLI client to start/stop asset streaming sessions (#4)

Implements the cdc_stream client and adjusts asset streaming in
various places to work better outside of a GGP environment.

This CL tries to get quoting for SSH commands right. It also brings
back the ability to start a streaming session from
asset_stream_manager.

Also cleans up Bazel targets setup. Since the sln file is now in root,
it is no longer necessary to prepend ../ to relative filenames to
make clicking on errors work.

asset_stream_manager/BUILD

@@ -9,6 +9,7 @@ cc_binary(
     deps = [
         ":asset_stream_config",
         ":session_management_server",
+        "//cdc_stream",
         "//common:log",
         "//common:path",
         "//common:sdk_util",