[WIP] tensorboard-notf for pytorch (re-submit of #1799)

[lanpa]

This modification let pytorch/pytorch@00b8330 use the code inside tensorboard installed by whl file build by bazel.

The generated event file can be rendered correctly by web server build from:
#1663

TODO:

• rename tensorboardX to something else (keep this name to avoid namespace confusion)
• correct way to handle plugin protos (now copy that directly)
• unittests
• fill license information to pass the test
• re-enable python2 build/test

[orionr]

@nfelt, we're getting closer on the split of tensorboardX into tensorflow/tensorboard and pytorch/pytorch. Would you mind doing a review here and give us some pointers on where the code should live? Much appreciated.

[orionr]

Can we use the version of this in the plugin directory instead?

https://github.com/tensorflow/tensorboard/blob/master/tensorboard/plugins/pr_curve/plugin_data.proto

[orionr]

Can we use the version in the plugin directory?

https://github.com/tensorflow/tensorboard/blob/master/tensorboard/plugins/custom_scalar/layout.proto

[orionr]

Same for this

https://github.com/tensorflow/tensorboard/blob/master/tensorboard/plugins/text/plugin_data.proto

[lanpa]

replaces plugin_text.proto and plugin_pr_curve.proto with plugin_data.proto will lead to name confliction. How about using soft links?

[orionr]

Instead of compat/tensorboard can we do compat/writer? @nfelt what are your thoughts on the right naming for this?

[orionr]

I think we can actually get all three of these from the plugins/ directory.

[orionr]

@lanpa, I just saw that you have direct reference of the protos on your TODO list. Excellent!