initial dev env setup scripts for Ubuntu and OSX (#8818)

Tools/setup/OSX.sh

@@ -0,0 +1,14 @@
+#! /usr/bin/env bash
+
+# script directory
+DIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
+
+brew tap PX4/px4
+brew install px4-dev
+
+# python dependencies
+sudo easy_install pip
+pip install -r ${DIR}/requirements.txt
+
+# Optional, but recommended additional simulation tools:
+brew install px4-sim