Deprecate GBIFResultsReader

[niconoe]

Since it's a moving, unstandardized target.

We have to make it easy to use DwCAReader for features currently in GBIFResultsReader.

We have also to clearly document this deprecation/removal cycle.

[niconoe]

As of March 2017:

• source_metadata features (the most important) have been moved to DwCAReader
• rights/citations properties have not, but the doc is updated in order to show how to easily access them

[niconoe]

• The doc aslo states it's deprecated.

Next step: remove?

[tucotuco]

I think it would be clean to remove it and better for maintenance.

[niconoe]

I think so!

So far, it's still working, but marked as "deprecated" in the doc, and the documentation in general has been updated to show the "new way". My idea is therefore to let it like this for a few months, then to simply remove it, for cleanliness and maintenance, as you suggested!

Does that sound like a good plan? Do you have any other suggestion?