Cmake changes and fixes to python script to get it to work properly

Mani reviewed most of this

First draft of cleaning up eventhost module on viewer shutdown.  Still need to make the whole system more generalized and data driven.

Fix for crash when running windows debug build.  std::string::replace cannot take NULL for it's argument.

Switching eventlet to use subrepo.

By Brad, reviewed by Palmer

Merged in my latest changes including switching LLAPRSockStream to be fully non-blocking (and thus not horribly inefficient) and a bunch of new event listener implementations.

Brad already added the LLCOMMON_LINK_SHARED definition. I removed the broken one I added and set the other one to ON by default.

Moveing around DLL copying to support building llcommon.dll and using llcommon.dll while running unit tests.

Added LLNotificationsListener to hook LLNotifications to the event system according to https://wiki.lindenlab.com/wiki/Incremental_Viewer_Automation/Event_API
reviewed by palmer.

Oops, forgot to update the plugin loading code when I switched ll_plugin_start to take LLSD arguments.

Add LLViewerWindowListener per Incremental_Viewer_Automation/Event_API.
Add LLViewerWindowListener pointer to LLViewerWindow, and initialize in ctor.
Add llviewerwindowlistener.{h,cpp} to newview/CMakeLists.txt.