Vulnerability - Problem with exported functions with identical taxonomy

[CatalinaYepes]

If different curves have the same taxonomy string, then the exported file do not differentiate among curves.

The specifications did not specify what to do in this case. I propose to add the function name when this happens.

See for example the exported file for the functions:

• https://platform.openquake.org/vulnerability/view/468/
• https://platform.openquake.org/vulnerability/view/469/
• https://platform.openquake.org/vulnerability/view/470/
• https://platform.openquake.org/vulnerability/view/471/