implement tab completion for dunecontrol

we install dune.complete into $PREFIX/share/bash-complete/
upto now you have to source the file by hand.
rename dune.complete to dunecontrol
move the completion file to $PREFIX/share/bash-completion/completions
add share to the subdirectories
[bugfix] distribute bash complition script
[buildsystem] Distribute CMakeLists.txt in tarball below share/.