shared: Move textfile detector to common

shared/common.h

@@ -1,7 +1,7 @@
 #ifndef COMMON_H
 #define COMMON_H
 #include <QCoreApplication>
-
+#include <QFileInfo>
 namespace Common
 {
 void setupAppInfo();
@@ -12,5 +12,6 @@ QString findInPath(QString needle);
 bool initSqliteDatabase(QString path);
 void ensureConfigured();
 QStringList excludedPaths();
+bool isTextFile(QFileInfo fileInfo);
 } // namespace Common
 #endif