fix typos in the release notes

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
mention opensrf_router managing its own PID file in release notes

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
cite the most relevant bug numbers for enhancements in the release notes

Signed-off-by: Galen Charlton <gmc@esilibrary.com>