By default, org-mode will add two spaces before code lines in the org
file itself. This does not change how code is edited when editing a
code block through `org-edit-special' but when copy/pasting code or
editing it directly from the org file, it can be troublesome.
Setting `org-src-preserve-indentation' to `t' prevents org from adding
these two spaces.
Rename `installation.org' to `bootstrap.org' since it better describes
what it is for.
Rename `emacs.org' to `spacemacs.org', preparing for the new
`emacs.org' dedicated to my vanilla config.
