Wiki code reorganization

This patch moves the Wiki related code more in one place:

 * Wiki specific code (search, refactoring) from fitnesse.components is moved to fitnesse.wiki.{search|refactoring}
 * PageFactory was taken by Descriptor, but not used.
 * Limit dependencies between wiki, wikitext and other packages. fitnesse.wiki and fitnesse.wikitext are still interlinked to some extend.