Add base type, plugin, attributes in JSON

  - Add BaseType and BaseTypeView for all type models/views from
    which they extend. They acting as base class.
  - Add capability to add plugins. Both CSS and JS. Plugins can give
    more flexibility to the app. JS plugins for creating dynamic
    components and CSS plugins for creating custom styles and design.
  - Add attributes field in the JSON, which can be used to specify
    attributes at the HTML element level.
Fix plugin

  Fix regexp in the Plugin model and other few issues.