[MERGE] Policy-based repository acquisition

[Andrew Bennetts]

Andrew Bennetts has voted tweak.
Status is now: Conditionally approved
Comment:
Looks fine.  As discussed on IRC, the Remote* special-casing should be 
removed by implementing set_make_working_trees.

I'm not totally sure if the bzrdir implementations test will actually 
use the right bzrdir format they way the override is done, but if you've 
double-checked that it's behaving sanely that's good enough for me.

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C47FD31C0.6000407%40aaronbentley.com%3E