- introduce 'DirectInterface' option to bind exactly to specified interface;
fixes#9666 and late IPv4/IPv6 address assignment
- option 'DirectInterface' takes precedence over 'Interface'
- improve interface/address handling,
e.g. verify count of listening endpoints due to dropbear limit (10 for now)
Signed-off-by: Konstantin Demin <rockdrilla@gmail.com>