Add docs for local Org mode to Info-directory-list
Use hooks, not advice, to modify org-store-link

Previously (4af0bf7), I used advice for org-store-link to make it store
notmuch links when called from Gnus buffers for local mail.

This now doesn't work because org-called-interactively-p returns nil if
org-store-link is advised. I'm assuming this is due to the nadvice
package, new with Emacs 24.4, which says

  FIXME: This Major Ugly Hack won't handle calls to called-interactively-p
  done from the advised function if the deepest advice is an around advice!
  In other cases (calls from an advice or calls from the advised function when
  the deepest advice is not an around advice), it should hopefully get
  it right.

Instead of using advice, create a separate function that will run a hook
before interactively calling org-store-link.
Don't let Org split current line
Respect Org content with all insertion commands