Add feature list to connection banner.

This allows us to test for features explicitly rather than relying on
the protocol version number, allowing us to fall back gracefully if a
feature is not supported.

This will be needed for the upcoming shell upgrades for stdout/stderr
separation and exit code reporting.

Change-Id: Ibb1d8ad2611f7209901ee76d51346b453e9c5873
5 files changed