[PATCH] Add zip format to export command

[Alexander Belchenko]

Goffredo Baroncelli wrote:
> the patch below add the zip format to the export command. 

It's funny. I'm already do similar job for my Windows version. But in
the end I decide to move zip exporter in to plugin. You can find my
plugin here:

http://bzr.onembedding.com/bzr.win/plugins/index.htm

For me the bad thing about zip format is no support for unicode names.
I'm thinking about use additional command line options for specify
filename encoding for non-ascii file names. It may be useful for some
cases when user definitely know what file encodings is. Something like this:

bzr zip-export --fe=cp866 dest.zip
                ^^^^ this is file name encoding option

Another limitation -- no symlink or empty directory support (latter only
limitation of python zipfile library) -- probably main reason why zip is
not included into mainline bzr.dev.

Alexander