Number of allowed subscription requests per minute

Be default filter allows 5 subscription requests to be sent from the single JID per minute. If some client will send more than 5 subscription requests it will be marked as a spammer.

Setting filter to allow 7 subscription requests per minute. 

'sess-man' () {
    'spam-filter' () {
        'presence-subcribe' () {
            'limit-per-minute' = 7
        }
    }
}