identity type
Implicitly, A hostSpec like "host" without "user@"
part matches only with peer host's identity
while "user@host" matches with any kind of identities.
By prefixing -iType before hostSpec, identities to be
matched can be specified explicitly. for example:
user@host
-- matches if at least one of identities is "user@host"
-h/user@host
-- matches if peer host's identity is "user@host"
host
-- matches if peer host's identity is "host"
-*/host
-- matches if at least one of identities is "*@host"
-a/host
-- matches if authenticated identity is "*@host"
-a/c/host
-- matches if authenticated or certificated identity is "*@host"
-a/*
-- matches if authenticated successfully