Cleanup CMakeFiles prior to release

* Remove Git revision finding code in favor of a simple command call: git rev-parse --short=7 HEAD
* Added GIT_HEAD_OVERRIDE to explicitly define the hash for the current commit in case git is not available 
* Made WIX default over NSIS in release tool 
* Rename version.h to git-info.h

src/gui/AboutDialog.cpp

@@ -20,9 +20,9 @@
 #include "ui_AboutDialog.h"
 
 #include "config-keepassx.h"
+#include "git-info.h"
 #include "core/FilePath.h"
 #include "crypto/Crypto.h"
-#include "version.h"
 
 #include <QClipboard>
 #include <QSysInfo>
@@ -47,8 +47,6 @@ AboutDialog::AboutDialog(QWidget* parent)
     QString commitHash;
     if (!QString(GIT_HEAD).isEmpty()) {
         commitHash = GIT_HEAD;
-    } else if (!QString(DIST_HASH).contains("Format")) {
-        commitHash = DIST_HASH;
     }
 
     QString debugInfo = "KeePassXC - ";

src/gui/CloneDialog.cpp

@@ -24,7 +24,6 @@
 #include "core/FilePath.h"
 #include "crypto/Crypto.h"
 #include "gui/DatabaseWidget.h"
-#include "version.h"
 
 CloneDialog::CloneDialog(DatabaseWidget* parent, Database* db, Entry* entry)
     : QDialog(parent)