api: implement reset call

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>
paypage: support multiple currencies

Litle provides one paypage_id per currency. Update the configuration
to support this and lookup the account currency when loading the Credit
Card form.

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>
paypage: allow currency override

This is mainly for testing.

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>