Fix a bug in arangodump for sharded edge collections.

Collection name in _from and _to fields was not reported correctly.

Conflicts:
	arangod/VocBase/replication-dump.cpp
Fix the fix of the arangodump bug in cluster.

Conflicts:
	arangod/VocBase/replication-dump.cpp
Improve error handling in arangorestore.

In particular:
  - Notice if collections mentioned in _from and _to fields of edges
    do not exist.
  - In cluster case make the coordinator report errors from the
    DBservers better.
  - Fail more quickly if arangorestore does not go well.

Conflicts:
	arangod/RestHandler/RestReplicationHandler.cpp
Mention arangodump/arangorestore improvements in CHANGELOG.