vmware-exporter missing metrics

[steled]

Hi,

it looks like that some metrics in the vmware-exporter are not correct/missing.

For some graphs I created a a PR #115 but for Memory Consumed it seems that vmware_host_mem_usage_average is not available in the original vmware_exporter.py.

The metric itself should be available by VMware, see mem.usage.average

So in general it would be great to fork the vmware_exporter repo or at least maybe just remove the graph.
What dou you think?