Use old-style <RestorePackages> settings to keep the TC build happy.
Fixed file path to Serilog.Extras.Timing.dll in nuspec.
Fixed timing assembly name. (Tweaked let the operation ID flow through as a scalar, opp. for sinks with a native GUID type to preserve it.)
Fixed the assembly name for the Loggly sink, hopefully getting its NuSpec to pack.
Implements the basics of #3 - XML configuration via AppSettings.
Fixes some issues with the app settings package (#3) that showed up with a bit more testing.