DispatcherInterface: * remove redundant functions. Let clients call dispatcherInstance() and do what they will with the AgentInstance they get. * implement dispatchManually ("send queued") and retryDispatching

Tests: added small programs that:

• use SendQueuedAction on the outbox (equivalent to DispatcherInterface::self()->dispatchManually())
• use ClearError on the outbox (equivalent to DispatcherInterface::self()->retryDispatching())
• tell the MDA to abort

svn path=/branches/kdepim/soc/kdepimlibs/; revision=982560