Make method naming more consistent.

* Use id() for methods returning a string used to represent
    some type of object.
  * Use displayName() for strings that are meant to be user
    visible.
  * Quieten some warnings while touching the files anyway.
  * Move Factories to their products in the plugins where that
    was not done before.

Reviewed-by: dt

src/plugins/git/gitversioncontrol.cpp

@@ -39,7 +39,7 @@ GitVersionControl::GitVersionControl(GitClient *client) :
 {
 }
 
-QString GitVersionControl::name() const
+QString GitVersionControl::displayName() const
 {
     return QLatin1String("git");
 }