Working on partial join operations in the planner.
Merge branch 'future/0.1.0' of github.com:Stratio/stratio-meta into future/0.1.0

Conflicts:
	meta-core/src/main/java/com/stratio/meta2/core/planner/Planner.java
	meta-core/src/test/java/com/stratio/meta2/core/planner/PlannerExecutionWorkflowTest.java