Use registry for Explorer context menu instead of NppShell

Instead of NppShell, you can set some values in registry for Explorer context menu:

```
[HKCR\*\shell\EditWithNpp]
@="Edit with Notepad++"
[HKCR\*\shell\EditWithNpp\command]
@="\"C:\\Program Files (x86)\\Notepad++\\notepad++.exe\" "%1" %*"
```
