Liferay IDE 2.0 updates for 6.1.x

Updated Liferay IDE content for chapters:
**2. The Plugins SDK** (very minor changes)
**3. Portlet Development**
**4. Generating Your Service Layer** (referenced event listing instructions in IDE chapter)
**5. Creating Liferay Themes**
**6. Creating Liferay Layout Templates**
**7. Hooks**
**8. Ext Plugins**
**9. Developing Plugins Using Maven**
**10. Liferay IDE**

https://issues.liferay.com/browse/LRDOCS-863
https://issues.liferay.com/browse/LRDOCS-864
https://issues.liferay.com/browse/LRDOCS-868
https://issues.liferay.com/browse/LRDOCS-879