Vcs: Some naming re-organization

Rename VcsCommand to VcsCommandTag, Command into VcsCommand
(Too generic to not mistake for Core::Command IMNSHO),
remove the now unneeded namespace qualification when not needed,
adjust surrounding code.

Change-Id: Iceb18a21e5e6dffa1a622241286f766985bb8d22
Reviewed-by: Christian Stenger <christian.stenger@digia.com>

src/plugins/git/clonewizard.h

@@ -44,7 +44,7 @@ public:
     CloneWizard(const Utils::FileName &path, QWidget *parent = 0);
 
 protected:
-    VcsBase::Command *createCommand(Utils::FileName *checkoutDir);
+    VcsBase::VcsCommand *createCommand(Utils::FileName *checkoutDir);
 };
 
 } // namespace Internal