Typesafe fields

[sidoh]

There should be a way to make an alternative to the _Fields enum which enables typesafe code. For example, we can have something like:

public static class _TypesafeFields extends JackFieldSet<Model> {
  public static final JackField<String> NAME = JackField.of(String.class);
  public static final JackField<Long> COUNT = JackField.of(Long.class);
}

which might be used in some kind of fancy type-safe query builder:

Set<Model> results = model.findBuilder()
    .where(Model._Fields.COUNT, 123L)
    .where(Model._Fields.NAME, "LiveRamp")
    .runQuery()

the where method might look something like:

public QueryBuilder where(JackField<T> field, T value) {
...
}

[tuliren]

This issue has been resolved by #141, which added typed columns and queries.