[PATCH 0 of 5] Revised shelve extension

[David Soria Parra]

Hi,

this is a revised version of the initial shelve extension series from
Bryan. I've fixed various bugs that I found, added more tests and tried
to incorporate feedback from the ML. The series

 (1) now use the VFS layer,
 (2) introduces a more compact listing format,
 (3) removes the unshelve command in favor of an --unshelve parameter,
 (4) makes shelve work with mq repositories.

Note: the last patch of the series (mq) relies on Pierres propertycache
fix in order to work correctly with MQ repositories.