Code review request for gadget-ui-editor

Branch name: gadget-ui-editor

Link to the relevant commit(s): 
https://code.google.com/p/oppia/source/detail?r=493760a82d76b981840c8d7a7385f42b
212b221d&name=gadget-ui-editor

Purpose of code changes on this branch:
- Basic implementation for EditorServices.js factories: 
explorationGadgetPanelsService and explorationGadgetsService.
- Console log confirms accurate panel and gadget instance details from factory 
initialization.
- 'Add Gadget' button in Editor UI logs a new gadget instance with properly 
generated unique name.

When reviewing my code changes, please focus on:
- Any recommendations on either factory, particularly the new 
explorationGadgetPanelsService API. Do the methods seem appropriate?
- Inline questions on the factory init() methods in particular.
- Squashed commits for an easier review. ~90% is relevant, but some code in 
skin_classes.py has already been reviewed. Just a heads up.

After the review, I'll merge this branch into: Nothing yet. Still working 
towards first end-to-end functional milestone.

Original issue reported on code.google.com by anu...@google.com on 25 May 2015 at 10:04

danieljjh / oppia

Code review request for gadget-ui-editor #779