Devguide ch02, 03

02-plugins-sdk
  - moved ## Creating Plugins to extend Plugins - to chapter 03.
  - minor edits.

03-portlet-development
  - Refactored Localization section, updating content on Resource Bundles (i.e., language keys). Used My Greeting Portlet in examples.
  - Added chapter summary.
  - Fixed typos in text and issues in examples.

@sez11a