Parcelport Cleanup

[sithhell]

The implementation of the various parcelports currently contains too much code duplication. In addition, the following tickets needs to be fixed in this process:

• refactor parcelport to allow better solutions for the remaining points (This has been completed with ea72168)
• hpx::naming::locality leaks parcelport specific information into the public interface #857: hpx::naming::locality leaks parcelport specific information into the public interface
• Create more versatile ibverbs parcelport. #840: Create more versatile ibverbs parcelport.
• Refactor ibverbs and shmem parcelport #839: Refactor ibverbs and shmem parcelport
• Implement zero-copy serialization for action arguments #812: Implement zero-copy serialization for action arguments
• Convert parcel ports into a plugin system #680: Convert parcel ports into a plugin system
• Parcels received before the early_parcel_sink is registered may cause problems #152: Parcels received before the early_parcel_sink is registered may cause problems