Add `to_dataframe` method to `ResultProperties` and `ResultShape`

[PierreRaybaut]

The purpose of this Issue is to add a to_dataframe method to the following objects:

• ResultProperties
• ResultShape
• (both inherits BaseResult class)

This to_dataframe method would simply return a Pandas dataframe for further result data manipulations.

ResultProperties.to_dataframe is already implemented since 3c3dc808e6021c2c89d465f7f6a72db8a62f72cf.

As for ResultShape class, we have to investigate further:

• It would be preferable to refactor this method to the base class BaseResult
• But, there is some inconsistency related to the way X-labels are created in those classes using get_xlabels (see # TODO comment in code)