API enhancements

Introducing a new employments endpoint.

A new employments endpoint has been added. Employment objects contain employment information including employment status, employment type, hire date, and termination dates.

The employment endpoint supersedes the employment-related fields returned in the profiles endpoint.

An employer field has also been added to all data set endpoints: profiles, employments, finances, reputations, documents, vehicles, payouts, activities. The employer field lists the company or entity that employs the user.