Implement the functionality of pairing BT device

[Blocking Requested - why for this release]: This is part of user story of FxOS 2.5 TV

In Gecko, BluetoothAdapter only allows bluetooth app (app://bluetooth.gaiamobile.org) to have pairingReqs https://dxr.mozilla.org/mozilla-central/source/dom/bluetooth/bluetooth2/BluetoothAdapter.cpp#318 In order to have this feature done, We might need to let device-deck to work with bluetooth app together.

WIP https://github.com/dwi2/gaia/commit/737f30566828b297c55013b14a700b064660e2bd

WIP is here https://github.com/dwi2/gaia/commit/7804eae9a19581be6dd0cd836e66b8077008d9d7 This WIP has done things below: 1. Make bluetooth_manager[1] as bower component because I also need it in bt-test[2]. 2. Remove bluetooth app from build/config/tv/apps-engineering.list because it is designed for phone. 3. Enable 'discoverable' and make device-deck able to receive pairing request system message. And the things still need to do are: 1. Display pin code when device deck receive pairing request and `displaypasskeyreq` event (we propagate it through BluetoothManager as `display-passkey-req` 2. Pipe pairing related tasks by handling `enterpincodereq`, `pairingconfirmationreq`, `pairingconsentreq`, `devicepaired`, `deviceunpaired`, and `pairingaborted` events. We may use some help with SmartDialog. [1]: https://github.com/fxos-bt-squad/bluetooth_manager [2]: https://github.com/fxos-bt-squad/bt-test/ [3]: https://github.com/smart-components/smart-dialog

There is one more thing. After bug 1192695 landed, we could set 'dom.bluetooth.app-origin' in pref to specify the only app that could do pairing. In our case, we should write this in build/config/tv/custom-prefs.js: user_pref('dom.bluetooth.app-origin', 'app://device-deck.gaiamobile.org');

Hi Rex, Can you help to find someone who can continue the work? Thanks!

Assign to myself for now.

Firefox OS is not being worked on