Feature - File extension inference

useful Feature.

When I launch Vezza with command VEZZA ZORK1 it would be good if it could infer the extension of the file. i.e. Doing a DIR ZORK1.Z* list exactly 1 file called ZORK1.Z3 thus it could check for this and launch the title.

Haveing to remember the extension is a little cumbersome, when in most situations it is likely there will be only 1 version of he file. In the unlikely event that there are 2 versions e.g. a Z3 and a Z5, then it could just error out as it does today.