Remap M-F7 to C-F7
Use `diminish' and (slightly) improve Emacs startup time

- To improve Emacs startup time, replace:

    (when (locate-library "pkg") ...)

  by

    (with-eval-after-load "pkg-autoloads" ...)

- Add key bindings for "multiple cursors".

- Replace ~/.emacs.d by `user-emacs-directory'.
Optimize startup time of Emacs

- Replace `locate-library' by `with-eval-after-load' (of the autoloads file).
- Remove some useless code.