Integrated support for visualizing/replaying flowtraces

[jonnor]

Flowtrace allows tracing FBP programs for retroactive debugging. It has a flowtrace-replay commandline tool, which replays the data as if it was a 'live' FBP runtime - so one can see the data in Flowhub.
However, it would be much more convenient if one did not have to run a separate tool for this but instead the feature was integrated in the IDE.

The flowtraces can be loaded from multiple different sources. By manually triggering a dump (see #524), from an fbp-spec run (see flowbased/fbp-spec#34), from an URL (see flowbased/flowtrace#2) (either copy/pasted/linked by user, or gotten through Flowhub registry/api).

[jonnor]

It would be nice to have URL scheme in Flowhub for this, so that one can just send a link to co-worker. Or have tools that output such a link, and one can open/copy/paste into browser.