Convert checkout_index to use progress callback
Convert checkout_* to use progress callback
Remove checkout_stats from git_clone
Remove dead code
Example: compile fixes (not yet working)
index: remove read_tree() progress indicator

git_index_read_tree() was exposing a parameter to provide the user with
a progress indicator. Unfortunately, due to the recursive nature of the
tree walk, the maximum number of items to process was unknown. Thus,
the indicator was only counting processed entries, without providing
any information how the number of remaining items.
Fetch/indexer: progress callbacks
Fix example compilation
Fix clone.c's indentation
Clone: in-line callbacks for progress

Also implemented in the git2 example.
Adjust for rebase
Correct progress reporting from checkout
Indexing progress now goes to 100%
Fix broken tests
gitno_buffer: callback on each packet

The fetch code takes advantage of this to implement a
progress callback every 100kb of transfer.
Remove third stage from checkout progress reporting

Also, now only reporting checkout progress for files that
are actually being added or removed.
Fix from rebase
Checkout progress now reports completed/total steps
Improve clone sample's formatting
tests: leverage git_repository_detach_head()