Make flagging of disconnected EDS graphs optional

[goodmami]

When a disconnected graph is serialized in EDS it gets a top-level annotation (fragmented) and the nodes disconnected from the top node are prefixed with |, but for the LKB this flagging is optional (according to an email with Stephan). The information isn't really necessary (analysis of the graph can reveal the disconnected parts) and is probably most useful for humans looking at the serialized output, so it should be toggleable with a flag.