Generate mappers for queries

[AlecKazakova]

If a sql_stmt inside the .sq file is a query, generate a custom mapper for it

[AlecKazakova]

Relevant: http://stackoverflow.com/questions/9114086/optimizing-access-to-cursors-in-android-position-vs-column-names

Once we know which columns we're grabbing and what order we can make mapping 20% faster woo!

[JakeWharton]

payments:
SELECT customer.*, payment.*
FROM ...

// generates:
interface Payments {
  Customer customer();
  Payment payment();
} 


payments:
SELECT customer.*, payment.*, COUNT(something) AS something
FROM ...

// generates:
interface Payments {
  Customer customer();
  Payment payment();
  long something()
} 


payments:
SELECT customer.*, payment.*, something.date
FROM ...

// generates:
interface Payments {
  Customer customer();
  Payment payment();
  Date date();
} 


payments:
SELECT customer.*, payment.*, something.date AS created_date
FROM ...

// generates:
interface Payments {
  Customer customer();
  Payment payment();
  Date created_date();
} 


payments:
SELECT sender.*, recipient.*, payment.*
FROM customer AS sender
JOIN customer AS recipient ON ...

// generates:
interface Payments {
  Customer sender();
  Customer recipient();
  Payment payment();
} 

[AlecKazakova]

a thought - instead of having the implementing class creating new mapper, potentially having to repeatedly specify column adapters, there could be a single factory class they instantiate which has paymentsMapper() : Mapper<PaymentModel> countMapper(): Mapper<Integer> marshal(): Marshal<PaymentModel> marshal(copy: PaymentModel): Marshal<PaymentModel> etc. methods.