* disable hardware-wallets that don't support libusb
* address grumbles
* nits
* Refactor to get rid off as much annotations asap
* Might consume slight more memory than pure conditional compilation
flags
* formatting nits
* Enable libusb for android
* Tested by it compiling succesfully with `cargo build --target=armv7--linux-androideabi`
* The binary is ~66 MB
```bash
$ size
size target/armv7-linux-androideabi/release/parity
text data bss dec hex filename
50676230 416200 31456 51123886 30c16ae target/armv7-linux-androideabi/release/parity
```
* Move all `fake-hardware-wallet` to its own crate
* Removes some conditional compilation flags
* Introduces `fake-hardware-wallet` crate
* return error if no hardware wallets are found
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