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)
 	}

cmd/mist/bindings.go

@@ -79,14 +79,14 @@ func (self *Gui) AddPlugin(pluginPath string) {
 	self.plugins[pluginPath] = plugin{Name: pluginPath, Path: pluginPath}
 
 	json, _ := json.MarshalIndent(self.plugins, "", "    ")
-	ethutil.WriteFile(ethutil.Config.ExecPath+"/plugins.json", json)
+	ethutil.WriteFile(self.eth.DataDir+"/plugins.json", json)
 }
 
 func (self *Gui) RemovePlugin(pluginPath string) {
 	delete(self.plugins, pluginPath)
 
 	json, _ := json.MarshalIndent(self.plugins, "", "    ")
-	ethutil.WriteFile(ethutil.Config.ExecPath+"/plugins.json", json)
+	ethutil.WriteFile(self.eth.DataDir+"/plugins.json", json)
 }
 
 // this extra function needed to give int typecast value to gui widget

cmd/mist/gui.go

@@ -100,7 +100,7 @@ func NewWindow(ethereum *eth.Ethereum, config *ethutil.ConfigManager, session st
 		plugins:       make(map[string]plugin),
 		serviceEvents: make(chan ServEv, 1),
 	}
-	data, _ := ethutil.ReadAllFile(path.Join(ethutil.Config.ExecPath, "plugins.json"))
+	data, _ := ethutil.ReadAllFile(path.Join(ethereum.DataDir, "plugins.json"))
 	json.Unmarshal([]byte(data), &gui.plugins)
 
 	return gui