#9 LJKit utilities

[Benjamin Ragheb]

Consider providing some optional utility classes/functions. Could
be useful as sample code. Maybe as a separate module.

1. An object that observes LJEntryWillSaveToJournal and
LJEntryDidSaveToJournal notifications and writes a text copy to a
temporary folder on disk, so that text isn't lost if the machine locks
up for some reason.

2. A function that installs the web menu in NSApp's main menu bar.

3. An image cache, for user pictures.