Fix POST, PATCH, DELETE with ?select= and empty body or return=minimal (#1471)

* add tests for POST, PATCH, DELETE when using ?select= with empty bodies or ret=min

* fix select with empty bodies and ret=min

* improved tests for default cases, fixed computed overloaded columns on empty-body?select= PATCH

CHANGELOG.md

@@ -10,6 +10,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 ### Fixed
 
 - #1473, Fix overloaded computed columns on RPC - @wolfgangwalther
+- #1471, Fix POST, PATCH, DELETE with ?select= and return=minimal and PATCH with empty body - @wolfgangwalther
 
 ## [7.0.0] - 2020-04-03