doc: online description of SKB and LKS
doc: online description of SKB and LKS

Closes #978

(With editting help from CJB)

keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client