Reapply "Implement new model for class members." and "Implement new model for interface members."

Reapply "Implement new model for class members." and "Implement new model for interface members."

BUG=
R=karlklose@google.com

Committed: https://code.google.com/p/dart/source/detail?r=31917

Committed: https://code.google.com/p/dart/source/detail?r=31964

[karlklose, 2014-01-17 14:18:05]

LGTM.

[Johnni Winther, 2014-01-17 14:43:02]

Committed patchset #2 manually as r31917 (presubmit successful).

[Johnni Winther, 2014-01-21 18:27:34]

PTAL @ the last patch

[karlklose, 2014-01-21 20:32:50]

LGTM.

[Johnni Winther, 2014-01-21 20:41:12]

Committed patchset #4 manually as r31964 (presubmit successful).