GC-81 add theme'nature' webpack.common.js and make nature.scss at resource/styles/agile-admin/inverse/colors and ../../scss/theme

config/webpack.common.js

@@ -30,6 +30,7 @@ module.exports = function (options) {
       'style':                './resource/styles/scss/style.scss',
       'style-theme-default':  './resource/styles/scss/theme/default.scss',
       'style-theme-default-dark':  './resource/styles/scss/theme/default-dark.scss',
+      'style-theme-nature':   './resource/styles/scss/theme/nature.scss',
       'style-presentation':   './resource/styles/scss/style-presentation.scss',
     },
     externals: {

resource/styles/scss/theme/nature.scss

@@ -0,0 +1,8 @@
+// import colors
+@import '../../agile-admin/inverse/colors/nature';
+
+// apply agile-admin theme
+@import '../../agile-admin/inverse/style';
+
+// override
+@import 'override-agileadmin';