SPipes validation constraint error should be outputed in a way that it is processable by client of s-pipes engine

[blcham]

The goal of this ticket is to be able to show validation errors within some UI.

Here is same example script that contains validations: https://github.com/kbss-cvut/s-pipes/blob/main/doc/examples/constraint-validation/constraint-validation.md

There are two types of validation constraints:

• ASK queries
• SELECT queries

Other requirements:

A/C:

• [x] both ASK and SELECT queries are handled
• [x] REST API returns validation error object in JSON-LD with context
• [x] log of the error is improved to show table (most likely it should use validation error object)
• [x] number of evidences is configurable in config-core.properties (default should stay as it is now)

[blcham]

@palagdan i improved description of this issue