Ethermint key generation (#78)

* WIP setting up Ethereum key CLI commands

* Functional key gen and showing Ethereum address

* Cleaned up changes

* WIP setting up Ethereum key CLI commands

* Functional key gen and showing Ethereum address

* Cleaned up changes

* Changed address to cosmos specific address

* Remove default bech32 prefixes and add basic add command test

* Changed Private key type to slice of bytes for compatibility and storability

* switch back to using cosmos crypto Keybase interfaces

* Changed key output to ethereum addressing instead of bitcoin and key generation to allow seeding from mnemonic and bip39 password

* Updated show command and added test

* Remove prefix requirement for showing keys and added existing keys commands to CLI temporarily

* Removed unnecessary duplicate code

* Readd prefixes for accounts temporarily

* Fix linting issue

* Remove TODO for setting PK to specific length of bytes (all functions use slice)

* Cleaned up descriptions to remove multi-sigs

app/test_utils.go

@@ -90,7 +90,7 @@ func newTestStdFee() auth.StdFee {
 // GenerateAddress generates an Ethereum address.
 func newTestAddrKey() (sdk.AccAddress, tmcrypto.PrivKey) {
 	privkey, _ := crypto.GenerateKey()
-	addr := ethcrypto.PubkeyToAddress(privkey.PublicKey)
+	addr := ethcrypto.PubkeyToAddress(privkey.ToECDSA().PublicKey)
 
 	return sdk.AccAddress(addr.Bytes()), privkey
 }