Add constructor with fields to generated beans

Automatically generate constructors with fields for generated beans. For instance:

declare Person
name : String @key
age : int @key
address : Address
end

For the above Person bean, generate:

• default constructor:

public Person()

{...}

* constructor with key fields:

public Person( String name, int age ) {...}

• constructor with all fields:

public Person( String name, int age, Address address )

{...}