Bugfix: arch list package building

Build packages for supported arches only. If a package only support x86_64 then
no attempt will be made to build a package for i686.
Bugfix: repo command only builds packages in stage

When using the repo command without "-p", only packages in the stage directory
will be added to the target repository.
Bugfix: delete old source files in repo target

When moving packages from the stage to the repo target, the old files were not
being deleted properly.
pbldr 0.3.3