Select language based on old notebook meta.lang.

Also fix UI when selecting kernels by string.

Fix  #7744 and  #7742

IPython/html/static/notebook/js/kernelselector.js

@@ -169,7 +169,8 define([
         var that = this;
         if (typeof selected === 'string') {
             selected = {
-                name: selected
+                name: selected,
+                language: selected
             };
         }
         if (this._loaded) {
@@ -246,7 +247,7 define([
         
         var body = $("<form>").addClass("form-inline").append(
             $("<span>").text(
-                "I couldn't find a kernel matching " + (data.selected.display_name || data.name) + "." +
+                "I couldn't find a kernel matching " + (data.selected.display_name || data.selected.name) + "." +
                 " Please select a kernel:"
             )
         ).append(select);

IPython/html/static/notebook/js/notebook.js

@@ -2209,13 +2209,20 define(function (require) {
         } else if (this.nbformat_minor < nbmodel.nbformat_minor) {
             this.nbformat_minor = nbmodel.nbformat_minor;
         }
-        
+
         if (this.session === null) {
             var kernel_name = utils.get_url_param('kernel_name');
             if (kernel_name) {
                 this.kernel_selector.set_kernel(kernel_name);
             } else if (this.metadata.kernelspec) {
                 this.kernel_selector.set_kernel(this.metadata.kernelspec);
+            } else if (this.metadata.language) {
+                // compat with IJulia, IHaskell, and other early kernels
+                // adopters that where seting a language metadata.
+                this.kernel_selector.set_kernel(this.metadata.language);
+                // this shoudl be stored in kspec now, delete it.
+                // remove once we do not support notebook v3 anymore.
+                del this.metadata.language;
             } else {
                 // setting kernel via set_kernel above triggers start_session,
                 // otherwise start a new session with the server's default kernel