Enable Drupal Views integration for Price Sets

New Feature Request:
Integrate price sets and price field data with Drupal Views.

Use Case:
Need to create event listings in Drupal using Views and that include information stored in price sets, such as registration fees and workshops.

Patch Info:
The attached patch adds a Price Set ID field to CiviCRM Events in Views.
In addition, it enables Views to be created on:

• CiviCRM Price Sets
• CiviCRM Price Fields
• CiviCRM Price Field Values
  It includes a Views Relationship between CiviCRM Price Fields and CiviCRM Price Field Values to make it easier to retrieve all of the values for a price field.

Usage:
Typical usage would be to create a view on CiviCRM Price Set or CiviCRM Price Field and pass in a Price Set ID as a contextual filter. The Price Set ID can be obtained as a field on CiviCRM Events. A Views Relationship can be added between CiviCRM Price Fields and CiviCRM Price Field Values to retrieve all of the values for a price field.