core, core/types: readd transactions after chain re-org

Added a `Difference` method to `types.Transactions` which sets the
receiver to the difference of a to b (NOTE: not a **and** b).

Transaction pool subscribes to RemovedTransactionEvent adding back to
those potential missing from the chain.

When a chain re-org occurs remove any transactions that were removed
from the canonical chain during the re-org as well as the receipts that
were generated in the process.

Closes #1746

cmd/geth/js_test.go

@@ -92,7 +92,7 @@ func testREPL(t *testing.T, config func(*eth.Config)) (string, *testjethre, *eth
 
 	db, _ := ethdb.NewMemDatabase()
 
-	core.WriteGenesisBlockForTesting(db, common.HexToAddress(testAddress), common.String2Big(testBalance))
+	core.WriteGenesisBlockForTesting(db, core.GenesisAccount{common.HexToAddress(testAddress), common.String2Big(testBalance)})
 	ks := crypto.NewKeyStorePlain(filepath.Join(tmp, "keystore"))
 	am := accounts.NewManager(ks)
 	conf := &eth.Config{