Remove bokeh dependency and obsolete UI views

[Flix6x]

Closes #405.

There should be some follow-ups we could discuss, like increasing our test coverage, and deciding on what info tooltips on the dashboard map should contain (or just link directly to the asset page).

[coveralls]

Pull Request Test Coverage Report for Build 2962650355

• 2 of 2 (100.0%) changed or added relevant lines in 2 files are covered.
• 331 unchanged lines in 13 files lost coverage.
• Overall coverage decreased (-2.6%) to 65.134%

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Files with Coverage Reduction	New Missed Lines	%
flexmeasures/data/models/markets.py	1	70.4%
flexmeasures/data/models/time_series.py	1	71.16%
flexmeasures/ui/crud/assets.py	1	74.15%
flexmeasures/utils/geo_utils.py	1	62.0%
flexmeasures/data/models/assets.py	8	71.29%
flexmeasures/utils/coding_utils.py	8	36.36%
flexmeasures/data/queries/utils.py	10	51.32%
flexmeasures/data/services/time_series.py	14	22.95%
flexmeasures/utils/time_utils.py	18	62.83%
flexmeasures/data/queries/portfolio.py	37	0%

Totals
Change from base Build 2947332461:	-2.6%
Covered Lines:	6475
Relevant Lines:	9336

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💛 - Coveralls

[nhoening]

Good start of removing things, we need to tackle this in more steps anyways, starting with the legacy data models.

I discovered that Coveralls is not showing you the source with changes (newly uncovered lines), unless you log in there (using your Github credentials).
Then, pages like https://coveralls.io/builds/51635571 become very useful to understand which parts of the code base are now uncovered.

[nhoening]

As it sits now, the space isn't being used. The title uses 9 cols, and the button below uses 3.
It leads to a lot of empty space on the right side.

Was that the intention?

And what would it take to display the current state in text form, as we discussed, e.g. "Current state: X% (of ".

Of course, the latter could also be done in a new ticket. But if it's small, this can be a good place as we are now taking that feature away. I might volunteer.

[nhoening]

@Flix6x mentioned there is still documentation in place mentioning plots which need Bokeh support (latest state?). That should be removed.

This ticket talks about removing tutorials needing Bokeh (this is about charts) and potentially moving to Altair for this useful feature.

This is the tutorial in question.

1. I propose we can leave the tutorial update to issue update chart plotting tutorial w.r.t. plotting #388, so this once can move on, helping us to also move on with dependency upgrades.
2. @Flix6x - can we keep supporting such a custom charting feature? I believe it would look more like an asset page (multiple plots of single sensor data), but plotted in a custom front-end.

[Flix6x]

can we keep supporting such a custom charting feature?

For sure. We already fetch charts using dedicated API endpoints, so it should just be a matter of moving them from the dev API blueprint to the v3_0 API blueprint, and adjusting the documentation.

I believe it would look more like an asset page (multiple plots of single sensor data), but plotted in a custom front-end.

They would look different (better imo) indeed. I believe the endpoint for fetching a sensor chart would be a closer replacement of the endpoint for fetching a "latest power state" chart than the endpoint for fetching an asset chart.

I think this PR should still get a changelog entry, and then it should be ready to be merged.