Add argument `action` as first positional argument, the second
positonal argument is for tests.
Add actions `doc` and `config`, doc works on org files and config works
on configuration file like packages.el.
The special action `all` performs all actions.
Move test files to `test` sub-folder.
Choose between `md5sum` and `md5` (on OS X) executables.
Add a new formatting function `move-packages-to-config` to move
package lists to config.el file.
