Fix income/pull with bundle and -R (issue 820).
Uses ui.setconfig() to tell bundlerepo where the main repo is. This is
needed for when the --repository option is used.
Adds tests to test-bundle and a new test script
test-mq-pull-from-bundle, which plays out the situation that initially
made me detect this bug
(hg -R .hg/patches pull ../bundle.hg).
% file replaced with directory
adding a
% should fail - would corrupt dirstate
abort: file 'a' in dirstate clashes with 'a/a'
% directory replaced with file
adding a/a
% should fail - would corrupt dirstate
abort: directory 'a' already in dirstate
% directory replaced with file
adding b/c/d
% should fail - would corrupt dirstate
abort: directory 'b' already in dirstate