Reflect pipeline outputs as well as inputs, optionally from other stages

* We add an option to reflect inputs from other stages than vertex, if only a
  later subset of the stages is linked into the program.

Test/baseResults/reflection.frag.out

@@ -0,0 +1,9 @@
+reflection.frag
+Uniform reflection:
+
+Uniform block reflection:
+
+Pipeline input reflection:
+
+Pipeline output reflection:
+