This exports the 'configuration' system as interface. It is not finally
settled if the filenames shall be *_interface.{c,h} and some details might
be sorted out (so far it works quite well).
This can also serve as example how to implement a slightly more complex
interface (some functions got inline wraped because we dont want to export
internal config system state).
This starts the proposed changes in
http://www.pipapo.org/pipawiki/Lumiera/DesignProcess/ApplicationStructure
* Moving all necessary files from src/backend to src/lumiera
* create a small helloworld main app
* setup the buildsystem to build it all
* fix include paths at many places
The testsuite is not yet fixed here, that will be the next commit
