Fixed FileGenerator::setUses() to allow passing in array of strings.

This patch allows setUses() to be called with an array of string 'uses'. This makes it easier to call when the 'as' part is not needed.

In my use case I had an existing array of strings that I wanted to pass directly to setUses().

This patch actually allows mixing of strings (without the 'as') and arrays of the form array('use', 'as') in the array that's passed to setUses(). This is demonstrated in testSetUsesWithString().