Show Exception Name in Shell Output

Currently, when the CLI encounters an exception, only the exception
message is shown.  However, the name of the exception can be quite
informative as well.

For instance, an error message might read "Cannot do xyz", which
simply indicates the operation was unsucessful.  However, the attached
exception name (HTTPNotImplemented, for instance) indicates the
*reason* that the call was unsuccessful.

Change-Id: I0298477bd9d40d98c95bb797c68c47dbc952b345
Print a useful message for unknown server errors

If a server error is returned that has an unknown code, novaclient will
end up printing something similar to:

ClientException: <attribute 'message' of 'exceptions.BaseException' objects>

Setting a message for ClientException will ensure that something more
useful than that is printed.

Change-Id: I43a2a33017f9a5c1b79d7fd8af4153e91d296f7b
Closes-bug: 1295293
Correct the help sting of volume-type-delete

Change-Id: I10b1bd6d42e4085dc73572f05ed893385ca3e139
Merge "Correct the help sting of volume-type-delete"
Merge "Show Exception Name in Shell Output"
Merge "Print a useful message for unknown server errors"