This change does three things:
* Splits out a WrappedException class from ApplicationException.
* Uses fail() pervasively rather than new ApplicationException() everywhere.
* Moves exception classes from utils.dart to exceptions.dart.

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//354663008

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@37713 260f80e4-7a28-3924-810f-c04153c831b5