Allowed non-default constructors for all plugins:
Changed MEF registration of plugins using custom PluginsUtility.RegisterPlugins instead of standard Autofac RegisterComposablePartCatalog.
Plugins locations for DeployPackages are now defined in .config file (compatible with Rhetos server).
Simplified use of IPluginConfiguration (for custom IoC component registration) - it is handled in FactoryModuleConfiguration instead of PluginsInitializer.
Refactoring of DatabaseGenerator:
Simplified use of plugins after switching to Autofac instancing instead of MEF.
Removed obsolete ConceptRepository.
Removed obsolete PluginRepository.
Merge pull request #6 from bantolov/master

Improved handling of plugins