Replace 204 response with empty map for get empty properties, fixes #83.

- This makes client-side code slightly simpler, since it removes an edge case
  entirely - just return an empty map for empty properties.
- The 204 response was undocumented, so this does not break documented
  behavior.
- Remove duplicate integration tests, replace with simple full-stack test.
Merge pull request #3436 from jakewins/2.2-restprops

Replace 204 response with empty map for get empty properties, fixes #83.
Docs: clarify location of remote shell settings.
Tiny rewriter that changes WHERE x IN [1] into WHERE x = 1
Make the page usage counter increments and decrements branch-free

This doesn't make much of a difference for performance, but I think it's neat none the less.
Merge pull request #3474 from systay/simplify-in

Tiny rewriter that changes WHERE x IN [1] into WHERE x = 1
Merge pull request #3475 from chrisvest/2.2-branch-free-page-usage-counter

Make the page usage counter increments and decrements branch-free
Merge pull request #3473 from jotomo/server-shell-conf-location

Docs: clarify location of remote shell settings.
Update GenericCaseTest.scala
Merge remote-tracking branch 'upstream/2.1-maint'
Refactored test code
stuff was changed
WIP