[15721] Support for Outer Join

[zhaoguoquan94]

This PR adds support for [Left | Right | Outer] JOIN queries in peloton's query optimizer.

Major changes:

• Replace InnerJoin* Rules with Join* Rules which support not only inner join transformation rules but also outer join rules. [rule_impls.h, rule.cpp]
• Add new Join operators [query_to_operator_transformer.cpp, operators.h,operator_node.h, internal_types.h]
• New physical plan generators[plan_generator.cpp].
• Bug fixes.
• Test cases.

Current Status

• two test cases still fails because old bug in optimizer. [planner_equality_test, optimizer_sql_test]
• Unknown bug in executor which generate incorrect results given correct plan.

[coveralls]

Coverage decreased (-0.07%) to 77.381% when pulling bb502225956988616db67e6b99d58f2badefbb51 on zhaoguoquan94:optimizer_project into f6446bab149da8aa85790f2a30ae74f40d9e1d87 on cmu-db:master.

[apavlo]

Good job. I am closing this PR. You can resubmit it at the end of the semester.

@nappelson @GustavoAngulo @dasteere Nice work.

[apavlo]

I decided to open this back up

[tli2]

Who is currently responsible for merging this in? Are code reviews here outdated or still being addressed?

[apavlo]

@saatviks is the PR czar this month.

[saatviks]

@apavlo I was last month - For June its @tli2