/**
@mainpage The KDevelop Extension Interfaces Library

This library contains extension interfaces used by KDevelop plugin architecture.

<b>Link with</b>: -lkdevelop

<b>Include path</b>: -I\$(kde_includes)/kdevelop/interfaces/extensions

\section whatisextension What is the KDevelop extension

Extension is a KDevelop plugin which implements one of extension interfaces.
Extension is usually not important enough to be returned by @ref KDevApi and @ref KDevPlugin
methods. Therefore extension instance can be obtained by @ref KDevPlugin::extension method.

Note: extension plugins can be either core, global and project plugins. They are loaded
in the same way other plugins are. But extensions differ from usual plugins.

Note: many plugins implementing extension interface can be created but only one of
those should be loaded at a time. This can be accomplished by:
- using a shell plugin profile (as done in current generic shell implementation) - define
  different X-KDevelop-Properties for different extension implementations;
- writing project manager which looks into the project file and loads the neccesary extension.

\section creatingextension Creating and using an extension
- Define a service, use following .desktop file:
  @code
  [Desktop Entry]
  Encoding=UTF-8
  Type=ServiceType
  X-KDE-ServiceType=KDevelop/MyExtension
  X-KDE-Derived=KDevelop/Plugin
  Name=My Extension Interface
  [PropertyDef::X-KDevelop-Version]
  Type=int
  @endcode
- Define an abstract base class for an extension like:
  @code
  class KDevMyExtension: public KDevPlugin {
  public:
      KDevMyExtension(const KDevPluginInfo *info, QObject* parent, const char* name)
          :KDevPlugin(info, parent, name) {}
      
      virtual void doSomething() = 0;
  };
  @endcode  
- Create an usual plugin, but instead of setting service type to "KDevelop/Plugin", set:
  @code
  ServiceTypes=KDevelop/MyExtension
  @endcode
- Use your extension:
  @code
  KDevMyExtension *myext = extension<KDevMyExtension>("KDevelop/MyExtension");
  if (sf) {
      // do something
  } else {
      // fail
  }  
  @endcode
*/