default client allowed ips in server config

[sphen13]

implementation of issue #32

i have never programmed in go - so please be kind :) in my testing this seems to do the trick. unsure if anything needs to be done in core/migrate.go

[vx3r]

nicely done! thank you @sphen13
i need to get rid of migrate.go file, it was initially to change data structure and make old json compatible with the new one, its a mess