tools: Rework how the js-lint and minify tools work

js-lint now cats the files together, and provides the input
to minify.

Install different minified and non-minified file names, for use
during debugging and non-debugging, and making use of the content
selection of minified files in the previous commit.
shell: This module becomes more normal

Rename cockpit.js to shell.js, since cockpit.js will be API in a
base package.

Also there's no need to list everything in the manifest. Loading
of resources happens via well known paths. The shell has such well
known paths. Loading of javascript in other packages will happen via
<script> tags. Do something similar here in the shell.

Note that the use of a lot of split javascript files that get
combined is pretty shell specific. Eventually we'll usually have one
javascript file per iframe/component to be loaded.

Closes #1319