Add verbose option

docs/data/Makefile

@@ -7,6 +7,17 @@ SPHINXBUILD   = sphinx-build
 PAPER         =
 BUILDDIR      = build
 
+# User-friendly check for sphinx-build
+ifeq ($(shell which $(SPHINXBUILD) >/dev/null 2>&1; echo $$?), 1)
+$(error The '$(SPHINXBUILD)' command was not found. Make sure you have Sphinx installed, then set the SPHINXBUILD environment variable to point to the full path of the '$(SPHINXBUILD)' executable. Alternatively you can add the directory with the executable to your PATH. If you don't have Sphinx installed, grab it from http://sphinx-doc.org/)
+endif
+
+Q_FLAG        = 
+
+ifeq ($(quiet), true)
+Q_FLAG = -q
+endif
+
 # Internal variables.
 PAPEROPT_a4     = -D latex_paper_size=a4
 PAPEROPT_letter = -D latex_paper_size=letter