SQL: new `ILIKE` operator to case-insensitively compare strings

As an alternative to manually lower case string comparison operands, a case insensitive`ILIKE` is a convenient operator to have,
so instead of:
```
SELECT name FROM doc WHERE name.toLowerCase() LIKE 'jOe'.toowerCase()
```
the `ILIKE` operator simplifies to:
```
SELECT name FROM doc WHERE name ILIKE 'jOe'
```