allow more chars in file names

[terraswat]

Currently we restrict file names to the characters:

a-z, A-Z, 0-9, dash (-), dot (.), underscore (_)

Chrome inserts "(1)" to make file names unique in the download area. This is no good when someone is trying the example and for some reason they download the file twice resulting in something like:

example_layout_features(1).tab

This file is rejected if the user tries to use it to create a map.