Major refactoring of scripts (preparing for multi-project distributions)

* Split old `scripts` into `.scripts` and `mosaic-scripts`.
* Add `tasks` folder (with symlinks to task generator scripts in either `.scripts` or `mosaic-scripts`).
* Split old `tasks-all.bash` into multiple chunks.
Update scripts

* Let `_do.bash` walk symlinks until it actually finds a link to `_do.bash`.
* Rename `pallur_pkg_mvn` to `pallur_pkg_maven`.
* Minor other fixes.
Add Mozilla JS and NSPR packages
Add two `_do-*` wrapper scripts
Add Mozilla JS and NSPR packages (older version used by Riak)