Vcs: Merge IVersionControl and VcsBasePlugin hierarchies

They were 1:1 in parallel, with quite a bit of function call
ping-pong inbetween, for code-sharing-by-inheritance. Merge
them by making VcsBasePlugin inherit IVersionControl and
merge the derived classes below.

Size of this patch is hard to avoid as all seven systems have to
move simultaneously. Non-necessary potential follow-up cleanup
have been left out on purpose.

Change-Id: Icb71e4182af3db21069cc637e7ae87ffa3829791
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/bazaar/bazaarclient.h

@@ -33,7 +33,6 @@ namespace Bazaar {
 namespace Internal {
 
 class BazaarSettings;
-class BazaarControl;
 
 class BazaarClient : public VcsBase::VcsBaseClient
 {
@@ -57,7 +56,6 @@ public:
     void view(const QString &source, const QString &id,
               const QStringList &extraOptions = QStringList()) override;
 
-protected:
     Core::Id vcsEditorKind(VcsCommandTag cmd) const override;
     QString vcsCommandString(VcsCommandTag cmd) const override;
     Utils::ExitCodeInterpreter exitCodeInterpreter(VcsCommandTag cmd) const override;
@@ -66,7 +64,6 @@ protected:
 
 private:
     friend class CloneWizard;
-    friend class BazaarControl;
 };
 
 } // namespace Internal