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 progress bar goes quickly up to 90% and then sits there for a while as the report is being written to the file. It would be better if
1) The baseIndex was less than 90, to make the progress bar more linear in time;
2) We could instrument the export functions to some extent to keep the progress bar moving forward during that time.