Edit Domain: consider bool as bool

[ajdapretnar]

• [ ] What's wrong?

  Box Plot doesn't show hidden attributes. But if one changes an attribute from hidden=True to hidden=False in Edit Domain, Box Plot still doesn't show the attribute, even though it was "unhidden".

• [ ] How can we reproduce the problem?

  Corpus - Preprocess Text (output only 5 tokens for ease of debugging) - Bag of Words - Edit Domain (change one attribute's label from hidden=True to hidden=False) - Box Plot. Box Plot won't show the attribute.

• [ ] What's your environment?

• Operating system: macOS

• Orange version: 3.28.dev

• How you installed Orange: git

[ajdapretnar]

The issue was in Edit Domain converting boolean values to strings.