StringFilterClause and ignoreCase

[adrianmroz-allegro]

After #1032, StringFilterClause has option ignoreCase that makes sense only for filters in CONTAINS mode. Rest of available modes ignore this setting.

Because we don't want to create new ViewDefinition version, we should leave FilterClauseDefinition objects in place. New field is optional with default value false. That's cool.

• We should create three new FilterClause classes for each string filter mode. Jest like with TimeFilterClause.
• Converters should handle validation and creation of specific class
• Fix all call sites for StringFilterClause - it will be only a Type, not a real class
• Add TypeGuard(s)