rtpproxy: add init script and UCI config

Signed-off-by: Jiri Slachta <slachta@cesnet.cz>
kamailio: add sleep time to init during restart

Signed-off-by: Jiri Slachta <slachta@cesnet.cz>
asterisk-11.x: update to 11.15.0, remove /etc/default/asterisk

Signed-off-by: Jiri Slachta <slachta@cesnet.cz>
asterisk-1.8.x: delete abandoned /etc/default/asterisk file

Signed-off-by: Jiri Slachta <slachta@cesnet.cz>