Add relative directory support to archiver

[stevenhl]

The archiver needs an option to allow creating zip with relative paths. Currently all paths are relative to the root.

One way to implement this is with a Mimimize paths checkbox. FM/2 would select a working directory that minimizes the store path.

Another way is to allow the working directory to be specfied and minimize the paths based on the selection. This supports cases where the user wants a top level empty directory to be included in the zip. This directory name is typically the application name and version.