support mapping specific java classe to custom TypeScript type declaration #76

(This is somewhat related to #11)

Instead of asking to emit TypeScript interface for specific Java type, allow specifying the TypeScript type declaration (and type name) to be used instead.

Couple of use-cases with examples:

Example 1

You might have some value-types in Java:

class PersonId {
  public Long value;
}
class CustomerId {
  public Long value;
}

and custom serializer+deserializer that unwraps the types, so that in TypeScript You should use it as a number:

type PersonId = number;
type CustomerId = number;
...
var personId: PersonId = 123;
var customerId : CustomerId = 456;

Example 2

You might have LocalDate class in Java, and want it to be aliased with JavaScript Date:

type LocalDate = Date;

Example 3

You might have LocalDate class in Java, and custom deserializer that can accept either string or number, so that in TypeScript You should be able to assign either of them to that type:

type LocalDate = string | number;