Changed ticker to use flat files rather than SQLite3

Also added update_tickerinfo.php for cron (rather than autoupdate via client)

@super3, you will need to set up a cron job to GET update_tickerinfo.php every x seconds (and perhaps add some access control). If you'd like I can make it enforce a minimum period between updates. I have tried to ensure this in git permissions, but ppcmarket.txt must be writeable by the PHP user.

Fixes #187