Board model - class style.
getChildren for boards is now a promise.all.
Prototype style methods.
Board model validation and legacy key support

Added Joi validation to the board model constructor. This validator
ensure all the correct properties are allowed through (only name is
required for now), and rejects any other keys.

Added support for generating legacy keys. Currently only SMF is
supported. The Legacy key is found in the getLegacyKey method on the
prototype chain.
Added tests for Board model. Minor Fixes

* Added tests for Board model constructor, getKey, getChildren, and
  getParent methods.
* Made changes to validator to accept children_ids array
* Updated all tests to rimraf their db after test completes
new agnostic constructor for Board.
Cleaned up models-board.js test. Fix getLegacyKey of Board Model.

* Moved where before is being run. Moved to top level of test suite.
* Changed getLegacyKey to call legacyKeyForBoard instead of keyForBoard.
Added support for smf metadata in Board Model Constructor. Added Test

* Now copying over smf data from what is passed into the Board model
constructor.
* Added test for getLegacyKey.
Updated boards test to correctly use test suite
Added board model to core boards crud

Started off by cleaning up the db references so that they are more
modular and readable. Also re-routed the index to point to the new board
controller file instead of the old board dir.

In the board model, validations were properly addressed. As well as, a
possible fix for catching promise error on validation. Also, the
getKeyFromId and getLegacyKeyFromId static methods were added and a
.prefix property that returns the prefix associated with this model was
added.

Tests were updated and cleaned of any extra console logs.
Fixed promise chaining for board model test
Model structure changes

Example for boards:
- wrapper is at /boards/index
- model is at /boards/model
- controller for db is at /boards/db
- reflects changes in /tests/model-tests //move later?
- core is currently exporting /boards/db for boards but should
  eventually export index.
Posts model + separated db

- db.insert now does key generation
Create/delete for posts with test.