dh override targets

dh override targets

* dh: debian/rules override targets can change what is run
  for a specific debhelper command in a sequence.
* dh: Redid all the examples to use override targets, since these
  eliminate all annoying boilerplate and are much easier to understand
  than the old method.
* Remove rules.simple example, there's no need to use explcit targets
  with dh anymore.