Support Dash-Renderer 2.0 - *Breaking Changes*

[chriddyp]

This PR updates the components to support the features introduced in plotly/dash-renderer#32.

Namely, it will enable various properties across various components to accept arbitrary dash components as values.

For example, the label property in dcc.RadioItems will be able to take a arbitrary Dash component instead of just a string.

i.e., instead of this:

dcc.RadioItems(
    options=[
        {‘label’: ‘Item 1’, ‘value’: 1},

        {‘label’: ‘Item 2’, ‘value’: 1}
    ]
)

the developer could do this:

dcc.RadioItems(
    options=[
        {‘label’: html.Div(‘Item 1’, style={‘color’: ‘cyan’}), ‘value’: 1},

        {‘label’: ‘Item 2’, ‘value’: 1}
    ]
)

This would require a dependency upgrade of dash-renderer to a 2.0 series, which would cause other component libraries that are not compatible with that version to break. There should be no breaking changes within this library.

This PR is a work-in-progress.

[chriddyp]

Prerelease versions are available with this code

pip install dash-core-components==0.16.0rc1
pip install dash-html-components==0.9.0rc1
pip install dash-renderer==0.13.0rc2
pip install dash-table-experiments==0.6.0rc1

[valentijnnieman]

@chriddyp Do we still want to keep this PR open, with regards to the new plan for 1.0 plotly/dash#469, and seeing as this is almost a year old?