.Net 4.0 support for Serilog.Sinks.ElasticSearch

Serilog.Sinks.ElasticSearch .Net 4.0 distribution is added to solution.
Serilog.Sinks.Seq package.config file was missing in the main
repositories, so its added.
Forgotten project file is added
Merge branch 'Net-4.0-support-for-Serilog.Sinks.ElasticSearch' of https://github.com/cihanduruer/serilog into cihanduruer-Net-4.0-support-for-Serilog.Sinks.ElasticSearch
By convention we keep packages.config files pointing to .NET 4.5.
Merge branch 'cihanduruer-Net-4.0-support-for-Serilog.Sinks.ElasticSearch'