Properties refactor

[dxg]

To fix #310 I needed a way to reliably pass a model property definition to a DML drivers valueToProperty method from within an Instance.
Since some properties were set on Model.properties whilst others like ids & association fields existed only in an array of strings (and their types were inferred by the drivers DDL sync code) this made life difficult.
It also introduced duplicate code, and issues with redefining key columns, and no good way to specify exact types for ALL columns.

I've come up with Model.allProperties which stores definitions of all constant properties (normal properties, id props, association fields). Extra properties remain separate as they are transient.

This allowed for some nice code cleanups in driver sync methods, and a simplification of opts.data initialization code inside Instance.

It also fixes some inconsistent behaviour I found along the way, like Model.create casting properties when they are set and instance.save not doing so.

Lastly, it introduces a new syntax (only internally for now) for defining keys, as discussed in #313 :

var Person = db.define("person", {
  id:   { type: 'serial', key: true },
  name: { type: 'text' }
});

Composite keys:

var Person = db.define("person", {
    firstname: { type: 'text', key: true},
    lastname: { type: 'text', key: true}
});

Keys are currently still set via the id property, however now that the underlying work is done, we can change this in future to the key syntax without too much pain.

Note: We now have both Model.allProperties and Model.properties. It should be possible to remove the latter in the future. It was taking me forever to finish this refactor, so consider this code a transition step.

@dresende the failing tests depend on sql-query 0.11.12 being published - the change in sql-query is small.

[dresende]

I just published sql-query@0.1.12. What happens if no key is defined in properties? Does the default primary key is used (defined or not as a property)?

[dxg]

Hmm looking at:

// ORM.prototype.define
id             : opts.id || this.settings.get("properties.primary_key"),

// Instance.js
    for (var i = 0; i < opts.id.length; i++) {
        k = opts.id[i];
        allProperties[k] = opts.properties[k] || {
            type: 'serial', rational: 'false', key: true, klass: 'key'
        };
    }

if someone defines id property without saying it's a key, it won't be a key.
Does that answer you question, or do you mean that we should set the defined properties key value to true at the end of the for loop?

[dresende]

What I meant was:

1. If no key defined, use default (usually id);
2. If no key defined but a property exists with the same name as the default id, use it (property type).

[dxg]

This PR doesn't change the behaviour. It's an intermediate step that allowed some code cleanups.

That said, I can work on part two (with key api changes) once this one is merged to keep things manageable.
Both 1. and 2. sound good, I will implement them in the next PR if we're happy with the proposed API.

[dresende]

Yes, go for it. Looks good to me :)