Pu/aggregation fix

[izulin]

Context

Numeric aggregation plugin was in a bad need for a refactor.
Reworked implementation captures the nuance of when values are coerced (mostly: when explicitly as a value-argument), and when are ignored when of wrong type (when passed as a reference or part of a range). Error propagation is also subtle: some functions ignore errors: COUNT, COUNTA.
Also, strings are coerced in a special way: string becomes always just a 0 (when passed as a part of a range/reference).

This PR also fixes handling of empty arguments in numeric aggregation functions (and in function MEDIAN).

How has this been tested?

See added tests.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature or improvement (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Additional language file or change to the existing one (translations)

Related issue(s):

1. Trailing commas #490

Checklist:

• My code follows the code style of this project,
• My change requires a change to the documentation,
• I described the modification in the CHANGELOG.md file.

[voodoo11]

👏