Fixed xfce4-terminal color.

* Extended the TERM-overriding logic added in recent commits to
  xfce4-terminal (COLORTERM=Terminal).

* Remove the previous workaround for broken values of TERM in .vimrc.
Vim ftplugin fixes.

- Changed Java back to 4-space indentation, which is universally
  conventional in Java (I have no idea why it was what it was before.)

- Make shell scripts use 4-space indentation.