Fix Firmware Update from Piksi Console

Fixes critical firmware update bug #89 and increases robustness of Piksi Console firmware update - should be able to update from any older firmware to any newer version, and also should be able to update if user's firmware is corrupted. Firmware update is now its own tab rather than a popup window.

Closes #113, #114, #111, #100, #89

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Took me a minute to figure out what this wait_count thing was about, perhaps this could be simplified?