[emacs] Set the smart-mode-line theme to nil.

This avoids having to decide on one.
[homedir] Replaced "``" with "$()" in shell scripts.

Apparently the backtick approach is deprecated.
[homdir] Quote shell variables where required.

This fixes many warnings for these scripts.
[install] Fixed several checks that were just wrong.
[emacs] Add hook for makefile-mode for tabs.
[emacs] Enabled line numbers in jam-mode.
[homedir] Whitespace cleanup.