Fix allowed filename chars

[Fraser999]

In windows the following are disallowed
|?*<":>+[]/

also the following filenames (in DOS even starting with these is bad sometimes ie com.h woudl fail)

CON, PRN, AUX, CLOCK$, NUL
COM0, COM1, COM2, COM3, COM4, COM5, COM6, COM7, COM8, COM9
LPT0, LPT1, LPT2, LPT3, LPT4, LPT5, LPT6, LPT7, LPT8, and LPT9.

In OS/x the colon : is also banned

I think our system should allow for all of these with
so in Linux if I create a david:.doc it should show as that always in linux and in win or OS/X I suggest change the name to
david(case conflict).doc

This keeps the file order and also allows the file still to be associated with the correct app (unlike dropbox which changes the extension which is poor).

For disallowed filenames I would have com for instance show up as com on Linux/OS/X and (name conflict)com in windows.