This patch adds support for a REST API for CRUD operations on traits.
GET /traits: Returns all resource classes.
PUT /traits/{name}: To insert a single custom trait.
GET /traits/{name}: To check if a trait name exists.
DELETE /traits/{name}: To delete the specified trait.
GET /resource_providers/{uuid}/traits: a list of traits associated
with a specific resource provider
PUT /resource_providers/{uuid}/traits: Set all the traits for a
specific resource provider
DELETE /resource_providers/{uuid}/traits: Remove any existing trait
associations for a specific resource provider
Partial implement blueprint resource-provider-traits
Change-Id: Ia027895cbb4f1c71fd9470d8f9281d2bebb6d8a2