Clash on bind hash value for query cache with consecutive values of "01","20" and "02", "10"

[rbygrave]

Steps to reproduce

    new EColAB("01", "20").save();
    new EColAB("02", "10").save();

    List<EColAB> list1 =
        Ebean.getServer(null)
            .find(EColAB.class)
            .setUseQueryCache(true)
            .where()
            .eq("columnA", "01")
            .eq("columnB", "20")
            .findList();

    List<EColAB> list2 =
        Ebean.getServer(null)
            .find(EColAB.class)
            .setUseQueryCache(true)
            .where()
            .eq("columnA", "02")
            .eq("columnB", "10")
            .findList();

    assertThat(list1.get(0).getColumnA()).isEqualTo("01");
    assertThat(list1.get(0).getColumnB()).isEqualTo("20");

    assertThat(list2.get(0).getColumnA()).isEqualTo("02");
    assertThat(list2.get(0).getColumnB()).isEqualTo("10")

[rbygrave]

The issue here being that the prime of 31 is a bad choice for hash collisions on consecutive values. Changing the prime used in the hash code calculation mitigates the issue but this needs a review. This will work for now but need to review and introduce a query cache bind key.