Disable hardware-wallets on platforms that don't support libusb (#8464)

* 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

rpc/src/v1/impls/light/parity.rs

@@ -305,8 +305,8 @@ impl Parity for ParityClient {
 	fn pending_transactions_stats(&self) -> Result<BTreeMap<H256, TransactionStats>> {
 		let stats = self.light_dispatch.sync.transactions_stats();
 		Ok(stats.into_iter()
-		   .map(|(hash, stats)| (hash.into(), stats.into()))
-		   .collect()
+			.map(|(hash, stats)| (hash.into(), stats.into()))
+			.collect()
 		)
 	}
 

rpc/src/v1/impls/parity.rs

@@ -34,7 +34,6 @@ use ethcore::state::StateInfo;
 use ethcore_logger::RotatingLogger;
 use node_health::{NodeHealth, Health};
 use updater::{Service as UpdateService};
-
 use jsonrpc_core::{BoxFuture, Result};
 use jsonrpc_core::futures::{future, Future};
 use jsonrpc_macros::Trailing;
@@ -53,7 +52,7 @@ use v1::types::{
 use Host;
 
 /// Parity implementation.
-pub struct ParityClient<C, M, U>  {
+pub struct ParityClient<C, M, U> {
 	client: Arc<C>,
 	miner: Arc<M>,
 	updater: Arc<U>,
@@ -143,11 +142,11 @@ impl<C, M, U, S> Parity for ParityClient<C, M, U> where
 			.collect()
 		)
 	}
-
+	 
 	fn locked_hardware_accounts_info(&self) -> Result<Vec<String>> {
 		self.accounts.locked_hardware_accounts().map_err(|e| errors::account("Error communicating with hardware wallet.", e))
 	}
-
+	
 	fn default_account(&self, meta: Self::Metadata) -> Result<H160> {
 		let dapp_id = meta.dapp_id();
 
@@ -312,9 +311,9 @@ impl<C, M, U, S> Parity for ParityClient<C, M, U> where
 		);
 
 		Ok(ready_transactions
-		   .into_iter()
-		   .map(|t| Transaction::from_pending(t.pending().clone(), block_number, self.eip86_transition))
-		   .collect()
+			.into_iter()
+			.map(|t| Transaction::from_pending(t.pending().clone(), block_number, self.eip86_transition))
+			.collect()
 		)
 	}
 
@@ -323,9 +322,9 @@ impl<C, M, U, S> Parity for ParityClient<C, M, U> where
 		let all_transactions = self.miner.queued_transactions();
 
 		Ok(all_transactions
-		   .into_iter()
-		   .map(|t| Transaction::from_pending(t.pending().clone(), block_number, self.eip86_transition))
-		   .collect()
+			.into_iter()
+			.map(|t| Transaction::from_pending(t.pending().clone(), block_number, self.eip86_transition))
+			.collect()
 		)
 	}
 
@@ -336,8 +335,8 @@ impl<C, M, U, S> Parity for ParityClient<C, M, U> where
 	fn pending_transactions_stats(&self) -> Result<BTreeMap<H256, TransactionStats>> {
 		let stats = self.sync.transactions_stats();
 		Ok(stats.into_iter()
-		   .map(|(hash, stats)| (hash.into(), stats.into()))
-		   .collect()
+			.map(|(hash, stats)| (hash.into(), stats.into()))
+			.collect()
 		)
 	}
 
@@ -345,9 +344,9 @@ impl<C, M, U, S> Parity for ParityClient<C, M, U> where
 		let transactions = self.miner.local_transactions();
 		let block_number = self.client.chain_info().best_block_number;
 		Ok(transactions
-		   .into_iter()
-		   .map(|(hash, status)| (hash.into(), LocalTransactionStatus::from(status, block_number, self.eip86_transition)))
-		   .collect()
+			.into_iter()
+			.map(|(hash, status)| (hash.into(), LocalTransactionStatus::from(status, block_number, self.eip86_transition)))
+			.collect()
 		)
 	}
 

rpc/src/v1/impls/parity_accounts.rs

@@ -22,7 +22,6 @@ use ethereum_types::Address;
 use ethkey::{Brain, Generator, Secret};
 use ethstore::KeyFile;
 use ethcore::account_provider::AccountProvider;
-
 use jsonrpc_core::Result;
 use v1::helpers::errors;
 use v1::traits::ParityAccounts;