Fix #456 & #461 (#491)

* Update setup.nsi
- Always display all language choices to fix #461
- Stop recursively removing installation directory as that
  is not a safe operation.  This may leave the installation
  directory after uninstallation but should be empty.  Fix #456.

* Update requirements-windows.txt
- Add pypiwin32 for cx-freeze as it was issuing a warning
- Prevent version 5.1.0 of cx-freeze as it produces non-working
  packages for some reason.  Version 5.0.2 and 6.0b1 work fine.

* Update setup to delete correct files

Installer will now delete the files in the installation folder along
with the folder if it is empty.  Bumped minimum cx-Freeze version to
5.1.1 as files are structured differently in older versions.

requirements-windows.txt

@@ -1,2 +1,3 @@
 PyQt5 >=5.4,<6.0
-cx-Freeze>=5.0.2,<6.0.0
+cx-Freeze>=5.1.1
+pypiwin32>=200

setup.nsi

@@ -222,12 +222,19 @@ Section "Uninstall"
   !insertmacro MUI_STARTMENU_GETFOLDER Application $StartMenuFolder
   RMDir /r "$SMPROGRAMS\$StartMenuFolder"
 
-  ; Delete the Install Directory and vendor directory (if empty)
-  Push $R0
-  RMDir /r "$INSTDIR" ;NSIS seems to recomend against this... look into options
-  ${GetParent} "$INSTDIR" $R0
-  RMDir $R0
-  Pop $R0
+  ; Remove Files & Folders in Install Folder
+  RMDir /r "$INSTDIR\help"
+  RMDir /r "$INSTDIR\imageformats"
+  RMDir /r "$INSTDIR\lib"
+  RMDir /r "$INSTDIR\locale"
+  RMDir /r "$INSTDIR\platforms"
+  Delete "$INSTDIR\dupeguru.exe"
+  Delete "$INSTDIR\python36.dll"
+  Delete "$INSTDIR\sqlite3.dll"
+  Delete "$INSTDIR\Uninstall.exe"
+  
+  ; Remove Install Folder if empty
+  RMDir "$INSTDIR"
 
   ; Remove registry keys and vendor keys (if empty)
   DeleteRegKey  SHCTX "${BASEREGKEY}"
@@ -246,6 +253,8 @@ Function .onInit
     SetRegView 32
   !endif
   !insertmacro MULTIUSER_INIT
+  ; it appears that the languages shown may not always be filtered correctly
+  !define MUI_LANGDLL_ALLLANGUAGES
   !insertmacro MUI_LANGDLL_DISPLAY 
 FunctionEnd