add removeKey and replaceKey methods

ts/smartssh.classes.helpers.ts

@@ -3,6 +3,10 @@ import plugins = require("./smartssh.plugins");
 import classes = require("./smartssh.classes");
 
 export let sshKeyArrayFromDir = function(dirArg:string):classes.sshKey[]{
-    let sshKeyArray = [];
+    let sshKeyArray = []; //TODO
     return sshKeyArray;
+}
+
+export let getKeyIndex = function(hostArg:string){
+    return 0; //TODO 
 }