Rename :import -> :_import_packages

This is to hide the function, because we would export it via
scripting aliases (/usr/bin/foobar -> internal function)
Rename :s-makepkg -> :_makepkg
- obsolete function :convert

This function is used to convert our old repository
(theslinux-buildsystem.broken.git) to the new one.
The new one is now working fine, and we do not need
this converting script anymore