This commit updates the design of the Web UI, with the following
changes:
* drop Twitter Bootstrap and the custom typeahead widget build
* use js-search, sass and a webpack build instead
* fully delegate version range management to the client application
* do not show the full list of dependencies anymore
This commit adds for now the packaged version of the application, but
this will change with gh-854 and the whole Web UI is likely to move to
start.spring.io proper.
