Add QueryExpression.LENGTH and QueryExpression.CONCAT operators

[sammyjava]

Details

This adds the LENGTH and CONCAT operators to QueryExpression, which can be useful. They were for me. :)

Testing

This update has been in production on the LIS mines for quite a while.

Checklist

Before your pull request can be approved, be sure to check all boxes:

• Passing unit test for new or updated code (if applicable)
• Passes all tests – according to Travis
• Documentation (if applicable)
• Single purpose
• Detailed commit messages
• Well commented code
• Checkstyle

[sammyjava]

Note: this shows three commits, but the first two are a forward and backward commit because I did a previous update on dev rather than creating a new branch as I should. The six files that are changed are indeed the six files that belong to this PR.

[sammyjava]

@danielabutano I need someone that understands the query testing system to fix the Travis test errors. I'm completely confused about where the error occurs and why. I've tried a couple times to fix it but I'm stabbing in the dark. Thanks. :) Not a high-priority PR in any case.

[danielabutano]

@sammyjava at the moment is the checkstyle which is failing, the tests have not been executed yet (the tests are executed after the checkstyle check). Looking at the commit you did, I noticd a lot of spaces not required or identation issues
I would suggest to fix the checkstyle first.
If you run ./gradlew checkstyleMain you can see locally what went wrong

[sammyjava]

@danielabutano Working on the checkstyle, but I know that I'll not be able to fix these subtle tests on the new query expressions. At least not without a massive amount of study. :) But I'll get the checkstyle cleaned up so that's all that's left.

[sammyjava]

@danielabutano I fixed checkstyle, but it'll still error on the tests which mystify me. But it's ready for someone who understands those tests to fix.