Add v1.0 Scheduler API

[oubiwann]

Official docs are here: http://mesos.apache.org/documentation/latest/scheduler-http-api/

Tasks:

• Implement Scheduler API JSON types - Implement Scheduler API JSON types #28
• Implement Scheduler Calls - Implement Scheduler Calls #7
• Provide Default Handler for Scheduler Events - Provide Default Handler for Scheduler Events #8

Part of epic #2

[wdhowe]

This is now complete: Implement Scheduler Calls - #7

[oubiwann]

NICE.