Query builder (#10104)

* add query builder to facilitate dynamic SQL construction

* leverage query builder to refactor user store

This is partially setup work for MM-13120, but merged to master to avoid
further conflicts.

* fix unrelated unit test breakage

* documentation tweaks

* Apply suggestions from code review

Co-Authored-By: lieut-data <jesse.hallam@gmail.com>

* prefer comma separated case options to fallthrough

* vendor github.com/Masterminds/squirrel and deps

* switch to using github.com/Masterminds/squirrel

* rm querybuilder

vendor/github.com/lann/ps/README.md

@@ -0,0 +1,10 @@
+**This is a stable fork of https://github.com/mndrix/ps; it will not introduce breaking changes.**
+
+ps
+==
+
+Persistent data structures for Go.  See the [full package documentation](http://godoc.org/github.com/lann/ps)
+
+Install with
+
+    go get github.com/lann/ps