Fix test for stack delete on same active engine

The test was not starting the EngineListener, thus the engine_id was
None, so the corresponding code execution path was not actually
exercised.

Change-Id: If48ba9d3deb54f8e9ea1ed1987f832ddbaed33fc
Correct example syntax and whitespace

Corrects some examples and remove trailing whitespace in
the Heat Resource Plug-in Development Guide
page (pluginguide.html)

Closes-Bug: 1350503

Change-Id: I34b142e950b9a4588b415d44274732d835cfd8f4
Client plugin exception handling methods

This change adds common methods which allow resources
to handle client exceptions without needing to directly
import the exception types.

The most common client resource exception handling is:
* Detecting if an exception is a 404
* Raising any exception which is not a 404
* Detecting if an exception is a 413 (over limit)
* Detecting if an exception was raised by a particular client
  library

Subsequent changes will move to using these methods.

Change-Id: Ib2bd55c31e66b562cfa8388beb450be6c06cc4fb
Merge "Client plugin exception handling methods"
Merge "Correct example syntax and whitespace"
Merge "Fix test for stack delete on same active engine"