Schemaless mode does not work with DIH

Schemaless mode does not work if you use DIH to index. This mode being most useful for prototyping, it makes sense to be able to use it with DIH, another great Solr tool that allows people to index some db content pretty fast.

I imagine this also affects other sources DIH can handle, not just SQL.

The issue is DIH code does not add fields it does not know so far, so the new fields to be added don't read the URP that adds them. A small change in DocBuilder.java was enough to fix this for my use case, now all my fields returned by the sql query are later added to the schema just fine.
I did not look in detail into multiValued fields, but maybe this small patch is enough for someone to look at it.