cache unipackage.load
Adjust source maps more efficiently at link time.
(Saves more than a second off of linking a small app!)
During development, don't reload packages that didn't change.
Saves about 150ms off development reload.
Rename "static" directory to "assets".
Replace "asset directory" concept with manifest of assets.

We were partway here already: the client served assets from the manifest instead
of from a static directory (since 5b8e1c1), and we already generated the list of
assets in the slice JSON file. But on the server, we ignored that list and
re-walked the asset directory at bundle time.

Now, the idea of asset directory is solely a part of initFromAppDir.

This also fixes a bug where assets that weren't associated with on-disk files
wouldn't work properly if Asset.get* is called in a package loaded with
unipackage.load. Not really sure how dev-bundle-fetcher even worked...

Also fixes a bug in builder where generated filenames didn't actually avoid
duplicate files.

This does not bump BUILT_BY because the previous commit did, and this commit
will not be pushed without the previous commit.
Rename "build version" to "built by" in other places too.
Be more conservative about soft library reload.
Only reuse a package if we still intend to be loading
it from the same packageDir.
Make galaxy configure command discover galaxy when a sitename is passed as an
argument.
dev bundle: use source-map version which took our PR.

Point to a slightly refactored version of source-map-support.

Have not yet bumped dev bundle version.
Upgrade fibers to 1.0.1. Specify the tested Node version in more places.

Dev bundle version not yet bumped.

Fixes #1153.
Update more NPM packages.

 - clean-css: 0.8.3 - 1.0.11
 - progress: 0.0.5 - 1.0.0 (includes the bug fix we requested)

Don't try to install source-map twice, oops.
Upgrade Underscore to 1.5.1.

A cursory glance at the diff suggests that this will not affect anything we do
in Meteor.
Bump dev bundle version.
Don't advertise 'meteor galaxy' command until Galaxy support is official.
Print error body if we get one from meteor mongo.

This got lost when we refactored to have the same interface as deploy-galaxy.
Add a note about how isServer doesn't strip code from the client.
Switch bootstrap tarballs to CNAME for CloudFront.
Add a comment about new Uglify version.
Move clean-css and uglify-js from dev bundle to a new minifiers package.

This will make it much easier to upgrade them and test new versions.

(They are still called from the bundler, so changes to how we access them (eg
source map support) will require modifying tools, but just "upgrade to new
version" now is much easier.)
Bump bundle version.