Auto reconnect and other improvements

Improvements

• Automatic network socket reconnection on startup (available in autoreconnect branch)
• Dead network socket peer detection with 'disconnected' event (available in autoreconnect branch)
• Pigpio errors returned with descriptive text strings
• Debug messages enabled through environment variable
  *Add version to info object

Patches

• Public API updated to reduce ambiguity.
• Code base changes to conform to public API.
• Fix gpio.notify updates current level only on first call.
• Fix exception thrown when gpio.endNotify is called without a callback.
• Fix to update current gpio levels when restarting notifications.
• Fix pigpio info properties not initialized before 'connected' event.