Expose validation metadata

The new Validatable.validations mixin method returns the validations as
an object
indexed by property name.
Applied Coobaha's PR fix - prevents undefined values
Validations configuration as object

Previously validations were appended to an array when configured. The
format was cumbersome, and led to issues. This refactors the
configuration into an object, as a property of the Model.

Note that if no validations have been configured, this property is
currently `undefined`.
Remove iteration of config args

Fixes #154 - args should only contain the property name at that point,
not loop over it.
Fix error messages, should be lowercase
Implemented Transient connector
Updated embedded relations to use transient connector

embedsMany will now use a connector's generated method, when defined.
Also, the id property type is now inferred correctly, making the autoId
option obsolete. However, a new option, forceId, can be set to enforce
the use of auto-generated ids, preventing any explicitly (user-)set id
values.
Enable dynamic modelTo for scopes

This is especially useful for relations/prototype scopes, as it allows
you to dynamically deduce the target model from the current receiver
(model instance). This is an advanced option that should otherwise have
no effect on the previous/default functionality. Basically, the
targetClass is taken out of the closure and handled by a method called
targetModel now.
Add hint, minor cleanup
Reset json when building model definition
Merge pull request #267 from fabien/fix/tiny

Fix error messages, should be lowercase
Merge pull request #272 from clarkorz/fix/polymorphicName-var-scope

fix polymorphicName var scope
Merge pull request #259 from fabien/fix/refactor-validations

Validations configuration as object
Merge pull request #268 from fabien/feature/transient-model

Transient connector implementation
Merge pull request #270 from fabien/feature/dynamic-scope-modelTo

Enable dynamic modelTo for scopes
Merge remote-tracking branch 'upstream/master'
Fix options for hasManyThrough doesn't apply

Signed-off-by: Clark Wang <clark.wangs@gmail.com>
Merge branch 'fix/through-params'