change default layout properties to have fewer top-level directories.

various source groupings (template files, files to include in intermediate artifacts, files to include in final distribution artifacts) are deprecated, and also moved to under the source dir, since they're all essentially sources.

similarly, the various kind of build output have all been moved under a "target" dir.  i'm adopting the name 'target' in preference to 'build' primarily because it seems broader and more approprate, and also partially out of deference to maven, as the idea that all output should be grouped is the one single concept that came out of maven that i find remotely agreeable.