Started adding the neccessary building blocks
From AST to Pipe through the new query planner

Added LogicalPlanner, QueryGraphBuilder and ExecutionPlanBuilder
Add new Planner into ExecutionPlanBuilder

This means that the new query planner now builds some type
of queries.
Merge pull request #2040 from systay/planner-bootstrap

First parts of the new plan building system
Move CSV loading from QueryContext to ExternalResources
Introduce observer pattern for Periodic Commit and Load CSV+Periodic Commit

o Document and test interaction between Periodic Commit and Load CSV
Refactor ExecutionPlanBuilder

o Broke out all state management into ExecutionWorkflowBuilder
o Add MappingBuilder
Disable commit row alignment for aggregation and union