Pivot from Mysql to SQLite for complex queries

[stemangiola]

I am not sure on how to produce proper feature request documentation, I will just describe it.

• get_metadata* add a class to the tbl instance (e.g. "CuratedAtlasQuery") to the existing classes.
• Add the method count (not redefining the generics). In that method we check whether the size of the ... parameter (columns to count) is > 1. Then we though error, pointing to get_metadata_local. If the count is on one column, we call the original count method with no changes
• Add the method collect (not redefining the generics). Through an error on this method for the moment.