by davidajnered, VoxPelli: Implemented single ping

by davidajnered, VoxPelli: Made XML-RPC ping work more like WordPress - two arguments only for method weblogUpdates.ping
by VoxPelli: Removed ping all option for now
by VoxPelli: Reconstructed the settings variables
by VoxPelli: Moved settings form to own page
by VoxPelli: Improved the menu items
by VoxPelli: Removed a few database calls
by VoxPelli: Tidied up code