groundwork
Add 'source-map' to dev_bundle and bump dev_bundle version.
(Consider this a preliminary version number, subject to
change, until this branch is actually merged.)
Source maps are generated, but they (1) are only
generated for server targets, not browser targets;
(2) aren't used for anything, (3) can only be generated
by linker (not by, say, coffeescript); (4) are stored 
incorrectly (inline in control files, rather than as
separate files); (5) are wrong anyway (at minimum, they
need to be adjusted for boundary string replacement
during link)

But hey. Source maps.
use a private dev bundle version number
rebase fixups
Add node-source-map-support to dev bundle.
Upgrade to newer source-map (same as what node-source-map-support uses).
Rename getLinked[Files/Output] -> getPrelinked$1
Correctly get the package name in the linker.
Write slice JSON with source map and sources as separate files.

We have not written the corresponding read code yet.
remove redundant use line
read fixed unipackage format
the path is packages/foo, not package/foo
Write sourcemaps and source files to JSImages.

Have not done the reading code yet.
Fix reading JS Images.
paths in program.json should not start with /.
Node stack traces are now rewritten based on (slightly wrong) source maps.

Also, assume that the program.json given to boot.js is relative to CWD, not
source file.
Source maps now are correct.

The header and footer of the linked file now is generated entirely at link
time. There is no more "boundary" __imports__asfdadsads blob.

Also, fix an inexplicable typo in js_analyze.
don't generate empty global import files
put js image format at top of file