Remove all demo-mode demos

[wchargin]

Summary:
See #1640. This removes all demos that instantiate a router in demo
mode. None of these demos worked: I loaded each one manually, and each
one failed to load some required resources.

Demos in plugins/graph and plugins/interactive_inference have been
allowed to stay, because (a) they actually work to at least some degree,
and (b) they do not use our router’s demo mode so are not posing any
obstacles.

For ease of review, this commit is a mass-deletion only. A separate
commit will include the structural changes that need to be made to
actually remove demo-mode.

Test Plan:
Check that routers are only created in the tf_backend implementation
and tests:

$ git grep --name-only createRouter
tensorboard/components/tf_backend/router.ts
tensorboard/components/tf_backend/test/backendTests.ts

Note that all existing tests pass in Python 2 and 3.

wchargin-branch: remove-demos

[stephanwlee]

Here are some weird traces of demo

➜  tensorboard git:(master) ✗ grep -r "@demo" tensorboard/* 
tensorboard/components/vz_chart_helpers/vz-chart-tooltip.html:@demo demo/index.html
tensorboard/components/vz_line_chart/vz-line-chart.html:@demo demo/index.html
tensorboard/components/vz_line_chart2/vz-line-chart2.html:@demo demo/index.html
tensorboard/plugins/graph/tf_graph_app/tf-graph-app.html:@demo demo/index.html
tensorboard/plugins/profile/google_chart/google-chart.html:@demo
tensorboard/plugins/histogram/vz_histogram_timeseries/vz-histogram-timeseries.html:@demo demo/index.html

Seems like google_chart one should remain the same though.

[wchargin]

Thanks! I didn’t know about those @demo annotations. To each:

• vz-chart-tooltip: this demo already didn’t exist; we can remove the annotation
• vz-line-chart: this demo works and doesn’t use demo-mode; we can keep it around
• vz-line-chart2: points to the same demo, which doesn’t use vz-line-chart2; we should remove this annotation
• tf-graph-app: this demo works and doesn’t use demo-mode; we can keep it around
• google-chart: this demo already didn’t exist; we can remove the annotation
• vz-histogram-timeseries: this demo works and doesn’t use demo-mode; we can keep it around

Will handle these as listed above unless you disagree.

Unrelated: my Travis build took 40 minutes to start.