Log Message:
Update to 0.5

The 0.5 release of Mono.Addins comes packed with new features, including:

 * User defined custom attributes can now be used to declare extensions
   and add-in metadata.
 * The new AddinEngine class allows hosting several independent add-in
   engines in a single application domain.
 * Improved lazy loading of add-ins. More information is now lazy loaded.
 * An XML manifest can now be split in several files embedded as resources
   in an assembly.
 * More add-in information can be declared using custom attributes instead
   of an XML manifest: author list, imported files and assemblies, optional
   modules, localizers.
 * Added new API based on generic methods and collections.
 * New MSBuild tasks file and target, which allows using add-in references
   directly in a build file (still experimental).
 * Reorganized the samples directory.
 * Many bug fixes.