Refactor dnsrecord processing
    
    Current DNS record processing architecture has many flaws,
    including custom execute() methods which does not take advantage
    of base LDAP commands or nonstandard and confusing DNS record
    option processing.
    
    This patch refactors DNS record processing with the following
    improvements:
     * Every DNS record has now own Parameter type. Each DNS record
       consists from one or more "parts" which are also Parameters.
       This architecture will enable much easier implementation of
       future per-DNS-type API.
     * Validation is now not written as a separate function for
       every parameter but is delegated to DNS record parts.
     * Normalization is also delegated to DNS record parts.
     * Since standard LDAP base commands execute method is now used,
       dnsrecord-add and dnsrecord-mod correctly supports --setattr
       and --addattr options.
     * In order to prevent confusion unsupported DNS record types
       are now hidden. They are still present in the plugin so that
       old clients receive proper validation error.
    
    The patch also contains several fixes:
     * Fix domain-name validation and normalization- allow domain
       names that are not fully qualified. For example --cname-rec=bar
       is a valid domain-name for bind which will translate it then
       as bar.<owning-domain>. This change implies, that fully qualified
       domain names must end with '.'.
     * Do not let user accidentally remove entire zone with command
       "ipa dnsrecord-del @ --del-all".
     * Fix --ttl and --class option processing in dnsrecord-add and
       dnsrecord-mod.
    
    All API changes are compatible with clients without this patch.
    
    https://fedorahosted.org/freeipa/ticket/2082