accounts/abi/bind: update v2 template

Two changes:

New function doesn't return error anymore. It's annoying having to handle
an error there, especially since we know the ABI must be valid (we parsed it in
order to generate the contract).

The new Instance method returns the ContractInstance for use with v2 library functions.

Author: fjl

accounts/abi/bind/source2.go.tpl

@@ -8,7 +8,7 @@ import (
 	"errors"
 
 	"github.com/ethereum/go-ethereum/accounts/abi"
-	"github.com/ethereum/go-ethereum/accounts/abi/bind"
+	"github.com/ethereum/go-ethereum/accounts/abi/bind/v2"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
 )
@@ -17,7 +17,6 @@ import (
 var (
 	_ = errors.New
 	_ = big.NewInt
-	_ = bind.Bind
 	_ = common.Big1
 	_ = types.BloomLookup
 	_ = abi.ConvertType
@@ -55,14 +54,20 @@ var (
 	}
 
 	// New{{.Type}} creates a new instance of {{.Type}}.
-	func New{{.Type}}() (*{{.Type}}, error) {
+	func New{{.Type}}() *{{.Type}} {
 		parsed, err := {{.Type}}MetaData.GetAbi()
 		if err != nil {
-			return nil, err
+			panic(errors.New("invalid ABI: " + err.Error()))
 		}
-		return &{{.Type}}{abi: *parsed}, nil
+		return &{{.Type}}{abi: *parsed}
 	}
 
+    // Instance creates a wrapper for a deployed contract instance at the given address.
+    // Use this to create the instance object passed to abigen v2 library functions Call, Transact, etc.
+    func (c *{{.Type}}) Instance(backend bind.ContractBackend, addr common.Address) bind.ContractInstance {
+         return bind.NewContractInstance(backend, addr, c.abi)
+    }
+
     {{ if .Constructor.Inputs }}
 	func ({{ decapitalise $contract.Type}} *{{$contract.Type}}) PackConstructor({{range .Constructor.Inputs}} {{.Name}} {{bindtype .Type $structs}}, {{end}}) []byte {
 		res, _ := {{ decapitalise $contract.Type}}.abi.Pack("" {{range .Constructor.Inputs}}, {{.Name}}{{end}})