Commented Task: Improve documentation [27836]

Current issues:
1. No automated generation of API reference
2. Missing docs for some extenders
3. Outdated content
Comments: The following tickets have been merged into this one: https://ajaxcontroltoolkit.codeplex.com/workitem/27672 https://ajaxcontroltoolkit.codeplex.com/workitem/7433 https://ajaxcontroltoolkit.codeplex.com/workitem/26809 https://ajaxcontroltoolkit.codeplex.com/workitem/11208 https://ajaxcontroltoolkit.codeplex.com/workitem/20532