Changed path of source resources to a project file related directory.

Actual scheme remains like this:

- Source related:
[project_file]/<live_extra_content_dir>

- Packages related (Source):
[project_file_dir]/<copyright>
[project_file_dir]/<file>
[project_file_dir]/<directory>

- Workspace related:
[project_file_dir]/<project_dir>
[project_file_dir]/<project_dir>/source
[project_file_dir]/<project_dir>/source/<repository_dir>
[project_file_dir]/<project_dir>/live
[project_file_dir]/<project_dir>/<tmp_dir>
[project_file_dir]/<project_dir>/<tmp_dir>/<package>
[project_file_dir]/<project_dir>/debian_installer

- Output related:
[project_file_dir]/<project_dir>/<project_name>.ext3
[project_file_dir]/<project_dir>/<project_name>-<arch>.iso
[project_file_dir]/<project_dir>/<debfiles_dir>

Notes:
  1. Relative paths are full paths if they start with a slash.
  2. 'project_dir' could be called 'workspace_dir'.