[debian] Update d/rules and switch to non-native package

Hi, I thniks we are good now :-D

* [x] Cleaned debian/rules by using python2 and sphinxdoc
* [x] Added debian/watch file
* [x] Override get-orig-source (remove .git and debian dir. from .orig tgz)

* [difference between a native/non-native](https://wiki.debian.org/DebianMentorsFaq#What_is_the_difference_between_a_native_Debian_package_and_a_non-native_package.3F)
* [why we need to override get-orig-source](https://wiki.debian.org/DebianMentorsFaq#What.27s_wrong_with_upstream_shipping_a_debian.2F_directory.3F)