Anki add-on: Increase autosave frequency

Makes Anki save every minute instead of every five minutes, customizable by configuring the add-on (editing the source on Anki 2.0). Additionally, adds a "save now" button on the file menu that does what it says. This add-on may be useful to those experiencing frequent crashes or the particularly paranoid. You almost certainly do not need this add-on anymore. Don't install it unless you're sure you do – it won't do anything useful and will add another possible point of failure to your Anki installation! Recent versions of Anki now save continuously except when working with legacy operations prior to the introduction of the new undo system (now mostly limited to old plugins). However, at user request I have updated it for the newest version of Anki, in case you still need it for some crazy reason.