Add support for exclude parameter

[zdenekjurka]

Motivation

Add support for new exclude query string parameter, that allows user to specify codenames of elements that should be excluded from API response.

Checklist

• [ ] Code follows coding conventions held in this repo
• [ ] Automated tests have been added
• [ ] Tests are passing
• [ ] Docs have been updated (if applicable)
• [ ] Temporary settings (e.g. variables used during development and testing) have been reverted to defaults

How to test

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 88.60%. Comparing base (e2045fe) to head (4553b37).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #391 +/- ## ========================================== - Coverage 93.26% 88.60% -4.66% ========================================== Files 129 130 +1 Lines 2775 2783 +8 Branches 349 346 -3 ========================================== - Hits 2588 2466 -122 - Misses 179 185 +6 - Partials 8 132 +124 ```

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