Cleanup expose loader configuration

We used to need to expose much more libraries for the premium plugin.
Some time ago we moved a lot of premium functionality to the free plugin
and we don't need to expose those modules any more.
[MAILPOET-3214]

webpack.config.js

@@ -71,30 +71,6 @@ const baseConfig = {
         exclude: /(node_modules|src\/vendor)/,
         loader: 'babel-loader',
       },
-      {
-        test: /form_editor\.js$/,
-        loader: 'expose-loader',
-        options: {
-          exposes: 'WysijaForm',
-        },
-      },
-      {
-        include: require.resolve('codemirror'),
-        loader: 'expose-loader',
-        options: {
-          exposes: 'CodeMirror',
-        },
-      },
-      {
-        include: require.resolve('backbone'),
-        loader: 'expose-loader',
-        options: {
-          exposes: {
-            globalName: 'Backbone',
-            override: true,
-          },
-        },
-      },
       {
         include: require.resolve('underscore'),
         loader: 'expose-loader',
@@ -197,13 +173,6 @@ const baseConfig = {
           exports: 'default Backbone.SuperModel',
         }
       },
-      {
-        include: require.resolve('handlebars'),
-        loader: 'expose-loader',
-        options: {
-          exposes: 'Handlebars',
-        },
-      },
       {
         include: require.resolve('velocity-animate'),
         loader: 'imports-loader',