ethutil: remove Config variable

Various functions throughout the codebase used it to grab settings. This
has to stop because I want to use them without reading the config file.

These functions can now be used without reading the config first:

* ethdb.NewLDBDatabase
* ethrepl.NewJSRepl
* vm.New

cmd/ethereum/repl/repl.go

@@ -54,7 +54,7 @@ type JSRepl struct {
 }
 
 func NewJSRepl(ethereum *eth.Ethereum) *JSRepl {
-	hist, err := os.OpenFile(path.Join(ethutil.Config.ExecPath, "history"), os.O_RDWR|os.O_CREATE, os.ModePerm)
+	hist, err := os.OpenFile(path.Join(ethereum.DataDir, "history"), os.O_RDWR|os.O_CREATE, os.ModePerm)
 	if err != nil {
 		panic(err)
 	}