Allow on the fly conversion to writeable file

[dedmen]

DokanPbo/DokanPbo.Core/PboFS.cs

Lines 262 to 263 in dd79448

	if (wantsWrite && !(node is IPboFsRealObject))
	return DokanResult.AccessDenied;

Let's say we edit a script file and press save, currently it's access denied, even though dokanPbo could make the directory writeable, and create a writeable copy of the file and then use that.

[dedmen]

Then we can also strip the "Readonly" prop from pbo files.
But we have to keep it on virtual pbo files like debin config.

We might not immediately want to convert once someone opens a file as writeable.
We only really need to do it once the actual write is done.