NMS-4763: Win2008R2 WMI TS stats fix and NMS-6822: add WMI disk/memory data collection

- Add WMI data collection points and graphs for memory paging (hard faults), WMI physical disk transfer rates, and WMI physical disk current and average queue lengths and busy/idle statistics
- Add win32_OS WMI data collection class and specific metric to get and graph the total amount of memory visible to Windows
- Add changed WMI class name for collecting Windows 2008 Terminal Server session statistics (NMS-4763, thanks to Daniel Hammon)