Include TREZOR support (Bitcoin hardware wallet)

Tails already includes Electrum bitcoin client which supports TREZOR bitcoin hardware wallet (bitcointrezor.com). In order to complete the support we need to do the following changes:

1) add package python-trezor (from testing or unstable)
2) add the following udev rule to system: https://github.com/trezor/trezor-common/blob/master/udev/51-trezor.rules

Original created by @stick on 10964 (Redmine)

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