[ADQL] Add ILIKE

src/adql/parser/feature/FeatureSet.java

src/adql/parser/grammar/adqlGrammar201.jj

src/adql/query/constraint/ComparisonOperator.java

src/adql/translator/ADQLTranslator.java

src/adql/translator/JDBCTranslator.java

src/adql/translator/MySQLTranslator.java

src/adql/translator/SQLServerTranslator.java

test/adql/parser/feature/TestFeatureSet.java