kcms/autostart: allow multiple entries and show absolute file paths

This commit:
- allows the user to create multiple entries for autostart (application or
  login script)
- shows absolute file path for login scrips along with their file name 
- fixes the issue of after adding a logout script it showed the file name
  for that specific script and then once the systemsettings is restarted it
  showed absolute path. Now it always shows the file name along with
  absolute file path