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>
The message on the Events view always says "Export failed", whatever went wrong. Is it possible to include a more helpful error message if we know what the problem was, for example "Could not open file {filename}"?