Projection aliases support for SELECT queries

[panarch]

Now the result of SELECT query returns both aliases and rows.
Implement support for fetching aliases.

e.g.

SELECT id, name as foo FROM TableA;

The query above provides not only fetched rows, but also it serve aliases like ["id", "foo"].

Change Payload::SELECT from

Payload::SELECT(Vec<Row>)

to

Payload::SELECT {
  aliases: Vec<String>,
  rows: Vec<Row>,
}

resolve #83

[panarch]

@willy610 Thanks for reporting this issue, now it works!

[willy610]

Nice implementation.

I think the public sql programmer in interfacing with the select thinks in terms of columns or labels or similar more than alias.

I think alias is more AST

Could be confusing also because all in the projection does not for sure have any AS NAME but sticks to the column name from a table.

Perhaps labels is preferred??

[panarch]

@willy610 That sounds... great.
I agree of the point you mentiond, alias sounds more.. related to AST, it may not fit to user-side names.

labels sounds good and I'll do work on this soon. thanks!