Iprove Dapp joining workflow

This is an improvement proposal related to the new configuration GUI tool.

I was wondering if we could also port the firmware update into the same configuration tool. We could have 2 tabs: one for **firmware**, the other for **configuration**, and have default files loaded from the same directory as the executable.

In this way, a developer could create one zip file containing everything needed for their DApp.

Their users only have to run the tool and click "Flash" if they need to flash the firmware or click "configure" to configure the pebble (no need to select any file if they are good with the default).

## The ideal workflow would be this one:

**Developer**
- Create a zip file containing the tool, the certificates, firmware, and the configuration file for their Dapp.

**Dapp user**
- Download the zip package from the developer website
- Run the tool (it will default to the firmware and configuration provided in the same directory)
- Click "Flash" in the Flash tab to flash the firmware if needed
- Click "Configure" in the configure tab to configure the device

## Even better workflow
This would require more changes to the firmware, but provide 1-click experience for the user (especially, they don't have to start the device in different modes):
- The user starts Pebble in Firmware update mode and only clicks "Configure" in the tool.
- The tool would flash the firmware, reboot Pebble in "Configuration mode", send the configuration, and reboot the Pebble in "normal working mode".