Create exerciserc to configure exercises

* Move timeouts from openrc to (new) exerciserc
* Update all exercise scripts
* Update HACKING.rst

Fixes bug 951315

Change-Id: Icc4ff03a7dcf0cc711e204046176fb5186990c17
diff --git a/exercises/bundle.sh b/exercises/bundle.sh
index 47bacac..0f128af 100755
--- a/exercises/bundle.sh
+++ b/exercises/bundle.sh
@@ -28,6 +28,9 @@
 # Import EC2 configuration
 source $TOP_DIR/eucarc
 
+# Import exercise configuration
+source $TOP_DIR/exerciserc
+
 # Remove old certificates
 rm -f $TOP_DIR/cacert.pem
 rm -f $TOP_DIR/cert.pem