network: hide vk-vpn-type for front-end
network: enable mppe default when add l2tp/pptp connection
network: enable to ignore ipv6 config
network: clear setting key errors that not available
network: use signal ConnectionDataChanged() instead of property Data
network: update test code
network: fix crash issue if ipv6 addresses and routes data type keep as interface{} when saving
network: fix ipv6 address issue, ignore redundancy errors
network: update nm_autogen
network: add manager_config.go, save and load configuration