DCworms

Added support for checkpointing

Added possibility to create checkpoints (with pausing and resuming).
Added possibility to load a task from the checkpoint.
Added CheckpointingPlugin interface.
Added abstract BaseCheckpointingPlugin.
Added checkpointing plugin to the scheduler definition and to the local management system.
Added checkpointing example with readme file.

Added possibility to get all the tasks from the job in the JobRegistry.
Changed event type comparison in Base plugin to comparison of the types names.
Changed connection of the event manager and the event handler to methods instead of events.
Added missing RELIABILITY_CHANGED event to reliability plugins.
Added reliability plugin initialization event when initializing computing resource.