Implementing constants for the job types used by EDP

Changes
* adding job type variables to sahara.utils.edp
* JOB_TYPE_HIVE
* JOB_TYPE_JAVA
* JOB_TYPE_MAPREDUCE
* JOB_TYPE_MAPREDUCE_STREAMING
* JOB_TYPE_PIG
* adding job sub type variables to sahara.utils.edp
* JOB_SUBTYPE_STREAMING
* adding job types list variables to sahara.utils.edp
* JOB_TYPES_ALL
* replacing string literals with edp job type variables
* removing get_possible_job_types from
sahara/service/edp/workflow_creator/workflow_factory

Implements: blueprint edp-job-type-constants
Change-Id: I8624dbdcd53814dcabdf3692ed3aa9547413226a
Merge "Implementing constants for the job types used by EDP"