Orange.data: Clean up the namespace

[lanzagar]

Issue

Orange.data namespace included a lot of junk.

Description of changes

Define __all__ in data.io.

Includes

• Code changes
• Tests
• Documentation

[kernc]

I don't think that's ok. The module defines a lot more "public" stuff than just Flags. Perhaps rather make import * in Orange.data.__init__.py explicit?

[astaric]

FileFormat might be considered public as well, as someone might use it to define their own readers, but what else? Reader implementations are not supposed to be used directly, they are accessible through FileReader.get_reader.

[lanzagar]

Added FileFormat. As said, the individual readers are really just current implementations that should not be used directly elsewhere, so I don't think they belong in __all__. And they can be imported from data.io if needed (for exceptional cases only).

[kernc]

but what else?

@astaric always more than one thinks.

https://github.com/biolab/orange3-text/pull/176/files

[codecov-io]

Current coverage is 89.05% (diff: 100%)

Merging #1813 into master will increase coverage by <.01%

@@             master      #1813   diff @@
==========================================
  Files            85         85          
  Lines          9029       9030     +1   
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
+ Hits           8041       8042     +1   
  Misses          988        988          
  Partials          0          0          

Powered by Codecov. Last update 002981b...05c1ef0

[astaric]

This is not really needed anymore.