SCVMM scheduled EMS refresh.

A mechanism was needed to refresh the SCVMM provider given that event support will not be in the 3.1 release. I have configured a 4 minute schedule but am open to negotiation on the frequency. On one hand we need to bear in mind that an EMS refresh can take more than 4 minutes but on the other hand we can't wait too long after a VM power operation.
@kbrock  @blomquisg 
to_i_with_method is for being able to have users specify the friendly rails methods in the config file:
"1.hour" instead of "3600"

I can't say I remember the code to know why overriding this was or wasn't a good idea.