CP-8866:Develop for Resource Statistic Feature on XenCenter

Based on the requirements draft and discussed solution, develop the prototype for Resource Statistic Feature part on XenCenter, that is, provide the export to Excel and CSV functionality with required data sets,by accessing the XenCenter cache.
Signed-off-by: Cheng Zhang <cheng.zhang@citrix.com>
We think it would be good to add some VDI data immediately below the SR data. Even if the customer didn't ask for it, it seems that they, or other customers, would want to know it to get a complete picture of their pool. We can list Name, Description, Size, and which SR they are on.