Added BT Connection Retry

- When a BT connection fails (which often happens when a device is lost and then re-discovered as described in #62 ) we now retry up to three times to reconnect the device. Seems like this always resolves the issue
- A device name can now be sent as part of the initial data.
- The device name that is sent with the initial data can now be set by the application via CWWebApplication setDeviceName: ; also the device name is now part of the app state
- The initial data now contains a dictionary that allows us to expand it with arbitrary data in the future without a lot of effort
- Added css to the valid file extensions in server.js
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