VcsBase: Hide VcsCommand class

Make it an implementation detail.
Introduce VcsBaseClient::createVcsCommand() method instead
for instantiating VcsCommands.

Replace all occuriences of VcsBase::VcsCommand in public API
with Utils::ShellCommand.

Change-Id: Ie438cc3a5e867b3ee8f9e935b56b2f16ea453f8a
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/vcsbase/vcsbaseplugin.cpp

@@ -27,8 +27,6 @@
 #include "vcsbasesubmiteditor.h"
 #include "vcsplugin.h"
 #include "commonvcssettings.h"
-#include "vcsoutputwindow.h"
-#include "vcscommand.h"
 
 #include <coreplugin/documentmanager.h>
 #include <coreplugin/icore.h>
@@ -40,19 +38,17 @@
 #include <utils/qtcassert.h>
 #include <utils/qtcprocess.h>
 
+#include <QAction>
 #include <QDebug>
 #include <QDir>
 #include <QLoggingCategory>
+#include <QMessageBox>
 #include <QSharedData>
 #include <QScopedPointer>
 #include <QSharedPointer>
 #include <QProcessEnvironment>
 #include <QTextCodec>
 
-#include <QAction>
-#include <QMessageBox>
-#include <QFileDialog>
-
 using namespace Core;
 using namespace Utils;
 using namespace ProjectExplorer;