Draft: Create a TangoAttr widget

Related to daiquiri!350 (merged)

This creating a TangoAttr widget with some configuration use cases.

• Supports a subset of tango types like int/float/string
• Allow to edit int/float only
• Allow to use the quality or the device state (or both to display the state)

On side note this also introduce device state selection for the documentation. The options available from the layout are displayed in the left (as yaml format), and on the right you can select one of the available mocked device state. As every options as always visible, it should be convenient for a documentation, and switching the state will help for the dev.