Merge pull request #53 from reneschuster/plugin-api-0.2.0

Plugin API 0.2.0 Fixed: Use of uninitialized value $pluginClass::
Plugin API 0.2.0: Small fix
Plugin API 0.2.0: Small fixes
Plugin API 0.2.0  Fixed: Exception on plugin deletion
Plugin API 0.2.0 Fixed: Use of uninitialized value $pluginName in concatenation (.) or string