Move all EC2 cred creation to eucarc

* Remove credential creation from files/keystone_data.sh
* Remove EC2 cert setup from openrc
* Remove sourcing of ec2rc from stackrc
* Collect the above in eucarc
* Allow rc files to be sourced from other directories; based on Chmouel's
  4881 proposal but is simpler and doesn't actually change the directory
* Create S3 endpoint
* Get EC2 and S3 endpoints from Keystone service catalog
* Add EC2 credential checks to exercises/client-env.sh
* exercises/bundle.sh and exercises/euca.sh use eucarc

Updates:
* remove readlink -f to stay bash 3 compatible
* use service catalog
* create S3 endpoint

Fixes bug 949528

Change-Id: I58caea8cecbbd10661779bc2d150d241f4a5822e
diff --git a/README.md b/README.md
index 34eb45f..e311bb8 100644
--- a/README.md
+++ b/README.md
@@ -41,6 +41,11 @@
     . openrc
     # list instances
     nova list
+
+If the EC2 API is your cup-o-tea, you can create credentials and use euca2ools:
+
+    # source eucarc to generate EC2 credentials and set up the environment
+    . eucarc
     # list instances using ec2 api
     euca-describe-instances