[New: openFATE 309347] Make build types pluggable

Feature added by: Adrian Schröter (adrianSuSE) Feature #309347, revision 1 Title: Make build types pluggable Buildservice: New Priority Requester: Important Requested by: Adrian Schröter (adriansuse) Description: Every special handling code for a certain build type needs to be become a plugin, to extend the OBS more easily and to read the code more easily. Currently we have * spec/rpm * dsc/deb * kiwi/all kind of live images * kiwi-product/SUSE product medias -- openSUSE Feature: https://features.opensuse.org/309347