Add `lazy` to the list of possible decorator properties

Originally reported by: Claudiu Popa (BitBucket: PCManticore, GitHub: @PCManticore?)

Until we'll have support for descriptors transforming methods into properties, we need to update the list of possible properties with a new member lazy.

Bitbucket: https://bitbucket.org/logilab/astroid/issue/279

pylint-bot / test

Add `lazy` to the list of possible decorator properties #279