HTML 5 User interface for the plugin

Iterate the UI of the PS export Plugin to create a production grade UI.

The current version is more about core capabilities.

1. Main Page
   1. Document details section (Done)
   2. Layer details Section(Done)
   3. Metadata controls (in-progress)
   4. Export and menu controls(Done)
2. Settings Page
   1. Photoshop settings section(Done)
   2. Document settings section(Done)
   3. Asset settings section(Done)
3. Overlays
   1. Overlay for messages. (Done)
   2. Export progress UI.(Done)