This change allows to import and use core modules from "debos" package and
actions from "actions" package. Add prefix 'debos.' to all symbols imported
from core "debos" package to satisfy syntax check.
Package "actions" shouldn't keep any common function or structure:
- function 'DownloadHttpUrl()' is moved from 'DownloadAction' to "debos"
package. New file 'net.go' has been added to keep a common network functions
in core part of debos.
- move common functions for extracting files from 'UnpackAction' to 'debos'
package. File 'archiver.go' has been added for common operations on archives.
Signed-off-by: Denis Pynkin <denis.pynkin@collabora.com>
