[Mono.Debugger.Soft] Caching VirtualMachine threads, caching frames in ThreadMirror and fetching StackFrames in bulk for all threads
Changed API for fetching StackFrames in bulk on multiple threads ThreadMirror.FetchFrames instead of automatically on VirtualMachine.GetThreads
Merge pull request #1048 from DavidKarlas/cacheThreadsAndBulkFetch

[Mono.Debugger.Soft] Caching threads and bulk fetching StackFrames