This method will return the full path to the json file for
a given asset name.

The field is optional

This is valid for assets like database and protocol template

This allows for code simplification and wider range of type
support.

Make it more flexible to avoid code duplication.

With the default implementation the first input is transformed
into a float so the next value written will go after the comma.

This avoids reloading the json_widget content immediately on
each keyboard input or mouse event (i.e. combobox mouse wheel
update)

This method will allow to check whether the content of the editor
is valid and continue further.

This will allow to more easily execute validation.

Updated tests

This allows the user to make better use of available space.

Test cleanup

Fixes #178

DescriptionWidget was over-engineering.

This decorator disable the possibility to add attributes to
to python objects outside the __init__ function.

Now:

- Only shows know assets subfolder
- Only show the version of the asset to edit

Part of #186
Replaces !51

The AssetWidget class shows the correct editor for the JSON
data to be loaded.

It also handles the saving part.