cleanup: bring code closer to community standards

various renames of variable names..

* vname -> chroot
* vensure -> ensure
* vtarget -> target

Explicitly add a "description" (with the same default).

bump version, since this is now imcompatible.
be more consistent in naming and style

use arrays for excludes, includes and components. Name them consistently
in plural, regardless of the commandline options to hint at the fact
that it *is* an array.
add documentation for all options