PerfView and TraceEvent 3.0-preview2

Action Requested: Please try this release and provide your feedback as issues in this repo, so that we can address any bugs and take your feedback into account on changes to the defaults. Please be sure start your issue title with "[PerfView 3.0]".

Fixes and Improvements:

• Fix missing changes to turn on some of the 64-bit file format improvements.
• Remove missed truncation code path for ETLX file generation in PerfView.
• Update progress text in PerfView when converting an ETL to an ETLX file.
• Update and simplify PerfView view group names.