FLUID-5439: Converted wiki page to markdown

Converted 
* http://wiki.fluidproject.org/display/docs/Connecting+the+Parts+of+a+Preferences+Editor to markdown
* http://wiki.fluidproject.org/display/docs/Tutorial+-+Creating+a+Preferences+Editor+Using+the+Preferences+Framework
* http://wiki.fluidproject.org/display/docs/Tutorial+-+Full+Page+Preferences+Editor
* http://wiki.fluidproject.org/pages/viewpage.action?pageId=26969033

http://issues.fluidproject.org/browse/FLUID-5439
In this paragraph, "modelChanged" should be code-ified (two occurrences).