Improve unexpected fields handling.

Improve unexpected fields handling.

Implement the UnexpectedField type. This is used
to handle unexpected key/value pairs found in
the environments.yaml file. The user will be able
to get rid of those fields just deleting their
values from in the interactive session.

Tests: `make check`.
No QA.

https://code.launchpad.net/~frankban/juju-quickstart/improve-unexpected-fields/+merge/199270

(do not edit description out of merge proposal)

[frankban, 2013-12-17 11:57:13]

Please take a look.

[matthew.scott, 2013-12-17 16:21:17]

LGTM, thanks!

[frankban, 2013-12-17 16:27:55]

*** Submitted:

Improve unexpected fields handling.

Implement the UnexpectedField type. This is used
to handle unexpected key/value pairs found in
the environments.yaml file. The user will be able
to get rid of those fields just deleting their
values from in the interactive session.

Tests: `make check`.
No QA.

R=matthew.scott
CC=
https://codereview.appspot.com/43380043

[frankban, 2013-12-17 16:29:26]

Thank you!