Use AIFilePicker everywhere.

Also upgrade the file picker filters with the new extensions found
in the orginal file picker code of Singularity.

Also improve AIFilePicker a bit: added hasFilename() and now
deleting the statemachine automatically by default: it's no longer
needed to call deleteMe from the callback.

indra/newview/lluploaddialog.cpp

@@ -161,10 +161,6 @@ void LLUploadDialog::setMessage( const std::string& msg)
 LLUploadDialog::~LLUploadDialog()
 {
 	gFocusMgr.releaseFocusIfNeeded( this );
-
-//    LLFilePicker::instance().reset();
-
-
 	LLUploadDialog::sDialog = NULL;
 }