PPL: bubble up values, bug fixes

[calebdoxsey]

Summary

Several changes for the Pomerium Policy Language:

1. Bubble up the values from rules to and, or, not and then to allow and deny. This is necessary because deny returns an HTTP status code and message.
2. Fix several rules where we were using = but should've used ==
3. Combine all the allow or deny rules into a complete definition using else blocks
4. Fix the databroker helpers so that they don't allow null values. We were doing this in authz but it didn't get ported over. Also use = instead of :=.
5. There was a bug in the user rule. It should be user.id not user_id.
6. Sort the rules and assign them locations so we get deterministic ordering of rules in the formatted output.

Checklist

• reference any related issues
• updated docs
• updated unit tests
• updated UPGRADING.md
• add appropriate tag (improvement / bug / etc)
• ready for review

[codeclimate]

Code Climate has analyzed commit 341ef2a and detected 1 issue on this pull request.

Here's the issue category breakdown:

Category	Count
Complexity	1

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