WIP: buffer name uniquification to allow shortening of dired-sidebar …

[retroj]

…buffer names

Partially addresses issue #99

Greetings,

I don't think this PR is ready to merge, but I would greatly appreciate a review.

This patch does not implement a buffer name shortening mechanism, but addresses issues of how buffer names are handled, to make shortening possible.

It also adds optional support for uniquification via uniquify.el with a new variable, dired-sidebar-use-uniquify.

I would still like to add a shortening mechanism, other than overriding dired-sidebar-buffer-name, but would appreciate any feedback as to whether I am on the right track so far with these supporting changes.

Thank you.