Changes to Search for LinkedIn job postings

the request property keywords became optional

the job_postings/items/date_posted response's property format changed from date-time to no format for status 200

removed the request property job_types

removed the request property work_types

added the new optional request property experience_level

added the new optional request property job_type

added the new optional request property sort_by

added the new optional request property work_type

the request property location became optional

added the new $140,000+ enum value to the request property salary

added the new $160,000+ enum value to the request property salary

added the new $180,000+ enum value to the request property salary

added the new $200,000+ enum value to the request property salary

added the new Any time enum value to the request property date_posted