Add DDI to Dataverse converter tool to Dataverse guides

[pdurbin]

Today @4tikhonov made a nice announcement of the DDI to Dataverse converter tool at https://groups.google.com/d/msg/dataverse-community/VoZP40fYlhM/iivwEQUCAgAJ

I'd like to suggest that this new tool could be added to future versions of the following pages (and perhaps more):

• http://guides.dataverse.org/en/4.16/api/native-api.html#import-a-dataset-into-a-dataverse-with-a-ddi-file
• http://guides.dataverse.org/en/4.16/api/apps.html#python
• http://guides.dataverse.org/en/4.16/developers/intro.html#related-projects

All the rst files are in https://github.com/IQSS/dataverse so please feel free to create an issue and pull request there.

I can also imagine a new page, maybe in the Admin Guide about migrating from various platforms to Dataverse. For example, there is the "Importing Nesstar DDI & data into Dataverse 4x" thread at https://groups.google.com/d/msg/dataverse-community/qsY8swD9Hh0/dnYi61g1AAAJ

[4tikhonov]

We also have a plan to create a new metadata schema(s) based on the DDI Study metadata, it can be managed directly with Dataverse API. This feature can increase the flexibility of metadata for the community and attract new data providers.