Add back thread debug prints / add better debugging for startup process

[drojf]

A while ago I removed the printouts (now gated by the Globals.DEBUG_THREAD_INFO variable) which state when threads are started/stopped by the installer, to clean up the installer output.

However in cases where the installer does not start up properly, this can make it difficult to debug.

It may be better to enable this output, and/or improve the output so it is more clear what tasks will need to be completed during the startup process.

Also, there should be some debug output / handling if a thread hangs completely for whatever reason.