gitconfig: simplify
dotfiles-clean: exclude mission-control (Empathy). Really remove files.

Also refactored should_remove(file) to split long boolean test into
multiple tests.
dotfiles-link: fix typo in variable name
ubuntu-defaults: simplify
inputrc: simplify
bashrc: simplify, do not fail if bash_completion or autojump is missing
gitconfig: renamed clean and really-clean aliases to cl and clr
Removed Mission Control (Telepathy/Empathy) configuration