Presents the user with an option to choose a file stored on their current platform (Windows/Mac only), for example a photo or sound file. If the user cancels the operation an empty string will be returned, otherwise the file will be copied to the apps current directory and the filename returned so that it can be used by your app.
You may specify an optional extension filter to limit the types of files the user will see when browsing. For example using an extension filter of "*.wav" would limit the user to choosing .wav files. For multiple extensions separate them with a semicolon like so "*.wav;*.mp3;*.png".
If using this command is used in tier 2 the returned string must be deleted when you are finished with it, even if it is an empty string. A null string will not be returned.
string ChooseRawFile( ext )