Enhancements to annotation class generation + prep for eraser functionality

[tamidodo]

• Removes the hover toolbar from the graph
• Adds the callback that will enable the eraser mode when we get a new release of plotly.py package
• Adds a "classes" key to the annotation-store data which has form {"increasing int": "class label"} where "increasing int" starts at 1 and is incremented upwards for each new annotation class.
• Restricts the user such that a new class cannot be generated with a colour or label that already is in use

Closes #34

[github-actions]

Staging application has been deployed and is available at: https://dash5-services.plotly.host/ml-exchange-staging
Production app name: ml-exchange
Current branch name: make-eraser-work
Commit: ea1cf28

[danton267]

great work with this!

Here is my feedback:

• while the user is in the modal for picking a color, every time they select new color the loading overlay triggers for half a second - it looks off
• would it be possible to select a newly created class automatically? right now user continues drawing with the old one
• can we change it so that max 4/5 labels are in one row, otherwise they start in the next row
• can you also store annotation color inside the annotation-store object, so that we can "load them back in" in the future when the user decides to continue with the project (don't worry about loading here, just store the color or whatever else is needed to create them)
• I don't think this was caused by this branch but on my PC, and multiple browsers, when I hover over the annotation tool images and the info tooltip pops up, the tooltip has a width of around 50px and dragged vertically ~one word in a line > yeah I saw that, it was caused by a previous branch, not sure which though and having trouble styling this.

[danton267]

@tamidodo on top of the features above, could you also add a "line" annotation option? Request by LBL

• Add a straight line annotation option

[tamidodo]

• delete all annotations associated with a class when you delete the class
• add a warning for deleting the classes
• add functionality to edit the class labels