beesh: Change sourcesubdir handling

add functions to set, append or prepend source subdirectories.

add_sourcesubdir is now deprecated in favor of sourcesubdir_append
beesh: Add functions to extract tar source archives
beesh: Improve filename guessing for fetched source archives
beesh: Minor cleanup
beesh: Add generic extraction functio bee_extract_do
beesh: Change the way source sub directories are handled

$S now points to the $W/source/souresubdirectory
beesh: Add support for zip source archives

To emulate the strip-components behavior of tar we scan
the extracted sources and prepend a sourcesubdirectory
if the archive is extracted into a subdirectory.

This is a much cleaner solution then to strip components out of
pathnames within the archive.

So tar extraction should be changed too in the future.