Values for keyaliases create --format option does not align with API

[kurtkanaskie]

keyaliases create --help shows:
-f, --format string Format of the certificate; selfsignedcert, pem or pkcs12 (file extn is .pfx)

API: https://cloud.google.com/apigee/docs/reference/apis/apigee/rest/v1/organizations.environments.keystores.aliases/create
Allows "keycertfile", "pkcs12" and "selfsignedcert"

Using the value of "pem" is equivalent to "keycertfile". apigeecli should use "keycertfile".

keyaliases get --help shows incorrect description for --alias option, shows "Name of the key store"