Assembly plugin to support 'directory' archive type

Add the ability for the assembly plugin to create an assembly on the native file system (i.e. a directory) that is not an archive (zip/jar/tar/etc).

The assembly plugin supports configuration of a directory structure containing pom dependencies and other files based on the specified assembly xml definition. Presently this is used to create various types of archives.

Using the assembly plugin is the only way I have found to create the correct directory structure for an application I am developing however I would like to do this without actually archiving the components (i.e. create the file structure but don't tar/zip/etc it). Building (and compressing) the archive takes a significant amount of time, and more often than not, we don't ever use the archive (except to extract the contents to the filesystem, run the application for testing, and never use it again), at least during development.

I propose adding a 'directory' archive type that simply copies the xml specified files/dependencies to a specified path. This archive type might be specified in the assembly xml file, or alternatively, via a runtime parameter (profile/property) overriding the archive type(s) specified in the assembly xml, for use during development.

I am currently working on a solution as this will be useful for our application that is built with m2, I will submit a patch as soon as I have something workable.