Add VMwareFrequency and VMwarePerfFrequency to all vmware.*.discovery

Now Zabbix asks users to set intervals for VMware metrics manually.

VMwareFrequency
Delay in seconds between data gathering from a single VMware service.
This delay should be set to the least update interval of any VMware monitoring item.

VMwarePerfFrequency
Delay in seconds between performance counter statistics retrieval from a single VMware service.
This delay should be set to the least update interval of any VMware monitoring item that uses VMware performance counters.

It would be nice to have the ability to set intervals automatically based on these parameters.