[ADF-theming-fix] Fix theming related issues (#2276)

* First steps

* Every package have separate entry points for styling mixins

* Moving to config dir, and using it in demo shell

* Remove webpack config include path magic from activiti-form package

* Fixing all the webpack common configs and using relative paths in the prebuilt themes

* Datatable header fix

* Update documentation

ng2-components/ng2-alfresco-core/config/webpack.common.js

@@ -64,10 +64,7 @@ module.exports = {
                 }, {
                     loader: "raw-loader"
                 }, {
-                    loader: "sass-loader",
-                    options: {
-                        includePaths: [ path.resolve(__dirname, '../styles')]
-                    }
+                    loader: "sass-loader"
                 }],
                 exclude: [/node_modules/, /bundles/, /dist/, /demo/]
             },