Fix a lot of String encoding issues on non-unicode systems

Renaming a folder causes the old folder to be removed
Fix some path separator issues on Win32
Fix file/folder opening in file browser on Win32

src/misc.h

@@ -57,6 +57,14 @@ public:
     return QString::fromLocal8Bit(str);
   }
 
+  static inline QString toQStringU(std::string str) {
+    return QString::fromUtf8(str.c_str());
+  }
+
+  static inline QString toQStringU(char* str) {
+    return QString::fromUtf8(str);
+  }
+
   static inline QString toQString(sha1_hash hash) {
     std::ostringstream o;
     o << hash;