ABS deps can now be built manually

- They are now checked recursively like AUR packages.
- This can be activated with the `--absdeps` long option.
Updated man page
Implmented `-Mc`

- Deletes the contents of the ABS Tree.
Before building, packages lists are now labeled AUR or ABS as appropriate
"Aura First" update style implemented - closes #97

- If there is an Aura update available, the user will be asked
  if they want to do it first. All other packages will be ignored
  for that session. They can then `aura -Au` again in a new session
  with the updated Aura.