net: shell: Add information about IPv6 configuration
net: shell: Add information about IPv6 configuration

The new "net ipv6" command which will print general IPv6 configuration
and information about autoconfigured IPv6 addresses.

Signed-off-by: Jukka Rissanen <f9f077d1da4c7aa947f9864fa5a28c3588f6a45d@linux.intel.com>

nashif/zephyr,ldts/zephyr,Vudentz/zephyr,galak/zephyr,Vudentz/zephyr,punitvara/zephyr,ldts/zephyr,finikorg/zephyr,nashif/zephyr,punitvara/zephyr,ldts/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr,Vudentz/zephyr,kraj/zephyr,Vudentz/zephyr,punitvara/zephyr,kraj/zephyr,explora26/zephyr,ldts/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,nashif/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,explora26/zephyr,galak/zephyr,galak/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,kraj/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,punitvara/zephyr,kraj/zephyr,nashif/zephyr,Vudentz/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,explora26/zephyr,explora26/zephyr