Default owner/group & permissions for file operations

[wbond]

Ticket #202 by vena:

It'd be wonderful if we could have a set once and forget method to default owner/group and permissions for files created by fFile, fORMFile, etc. Outside of an suPHP environment, this can be quite necessary if you ever want to manipulate files created by the script by hand.

Comment by @wbond:

Due to the way that file permission are set up, the owner of a file can only be changed by the superuser. The group can only be changed to a group that the user, that the web server is running as, is part of. Because of those limitation it doesn't look like it will be possible to set that up.

In terms of the file permissions, I think I can come up with something. Currently fUpload chmods all uploaded files to 0644, but it would be good for fFile::create() and fDirectory::create() to all obey one set of permissions.