[dev] Count Shares patch

[Chuck Hagenbuch]

Quoting Duck <duck at obala.net>:

> Attached is a patch to add count method to Shares. I need it for Genie to
> determinate the number of shares available. Otherwise we must have a
> wastefully operation of selecting thousand of shares just to find out that
> they are to many and we should switch to a custom wishlist selection. I
> belive counting can be very useful in elsewhere.

This won't help us with apps compatible with Horde 3.0, but it's fine  
for new code, and something we can take forward into the new share  
API. Committed, thanks.

-chuck