Implement Service-Oriented Deep Dependency Graph (DDG)

[everett980]

This is a tracking issue to encompass the work done across many PRs to get the first revision of the DDG into JaegerUI.

Brief overview of functionality covered in first revision:

• Users can view a graph of DDG paths aggregated by a flink job.
• Users can specify density heuristics.
• Users can group operations for a service.
• Users can expand/shrink the visible portion of the graph by selecting how many hops to view.
• Users can also search for services or operations in the graph, and show matches outside of the current hop boundaries.
• Users can mouse over a node to emphasize all paths through that node.
• Users can view exemplar traces for a given node.
• Users can navigate between DDGs.
• Users can share links to a DDG, preserving essential parts of UI state.

List of PRs by author:
@tiffon in #442, #441, #440, #439, #438, #437, #431, #406, and #405
@everett980 in #468, #466, #458, #463, #457, #453, #452, #434, #433, #432, #429, #427, #424, #421, #412, #398, #386, and #378