as mentioned [here][1] some firmwares require to reset all settings.
this commit add a param "keep_settings" which changes the sysupgrade
parameter "-c" to "-n" to flush all configs

[1]: https://github.com/aparcar/gsoc17-attended-sysupgrade/issues/34

Signed-off-by: Paul Spooren <paul@spooren.de>

add ubus call to perform a sysupgrade and acl file for the attended
sysupgrade use case as well uci defaults.
Package is a part of the GSoC 17 project implementing easy
sysupgrade functionality.

Signed-off-by: Paul Spooren <paul@spooren.de>