Improve file name validation

[jasonsanjose]

There are some filenames like COM1, LPT3, etc. that are not valid on Windows. We may want to add checks for those here. See http://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx

[njx]

QRB reviewed.

[peterflynn]

The experience doesn't seem too awful today: if you do File > New and try to use one of those filenames, you'll get an error saying 'Invalid file name. The file already exists.' This is already pretty similar to the validation error ('Invalid file name. Files names cannot contain the following characters: ...').

[redmunds]

FBNC to @jasonsanjose.

[jasonsanjose]

Confirmed. Closing.