Changeset 16984 for branches/2924_DotNetCoreMigration/HeuristicLab.PluginInfrastructure/3.3/Exceptions

#2924:

• merged projects HeuristicLab.PluginInfrastructure.Runner and HeuristicLab.PluginInfrastructure
• applied changes of code reviews (13.05.2019 and 22.05.2019) -> the old Runner is now RunnerHost and uses a Runner, which is executed on the child process
• added Type GetType(string) to IApplicationManager and implemented it for LightweightApplicationManager
• removed IActivator and IActivatorContext
• deleted unused types like PluginDescriptionIterator