js: try new prettify-symbols-mode in Emacs 24.4

However, this is not quite what I had previously.
prog: use pretty-mode (just to try out)
org: don't output clock date with number of days

Always use hours.
org: replace stuff like \emsp by the appropriate symbol
files: allow to open files with line/col at the end
files: also allow to open files with line/col from emacsclient