Add loadByPid() to ObjectService

[Dave Reid]

It would be nice to load individual objects by pid. And if the pid to internal ID would be cached as well so that the next time I wouldn't have to do another HTTP request.

[Dave Reid]

Resolved with https://bitbucket.org/lullabot/mpx-php/commits/4aba07057009c94113a51bf5150684997dee28f6

[Dave Reid]

Also, learned that normal objects do not include their PID values.

[Dave Reid]

Huh, so Media objects do not include a pid, but Player objects do. WTF.

[Dave Reid]

Ah, Media 1.7 schema now includes pid. Resolved.