[PATCH 0 of 2] introduce store classes

[Adrian Buehlmann]

This two patch series provides a refactoring for Mercurial which
introduces classes for the store, as last discussed in the subthread
starting at
http://selenic.com/pipermail/mercurial-devel/2008-July/007233.html
(Matt's general ok:
http://selenic.com/pipermail/mercurial-devel/2008-July/007234.html)

I've moved the exception catching as suggested by Dirkjan in
http://selenic.com/pipermail/mercurial-devel/2008-July/007236.html

This patch series is quite well tested and is ready for inclusion
from my side. I did run the testsuite on FreeBSD.