libobs: Add file saving to file property

(This commit also modifies the UI)

Closes jp9000/obs-studio#502

libobs/obs-properties.h

@@ -72,6 +72,7 @@ enum obs_combo_type {
 
 enum obs_path_type {
 	OBS_PATH_FILE,
+	OBS_PATH_FILE_SAVE,
 	OBS_PATH_DIRECTORY
 };
 

obs/properties-view.cpp

@@ -1496,6 +1496,10 @@ bool WidgetInfo::PathChanged(const char *setting)
 		path = QFileDialog::getOpenFileName(view,
 				QT_UTF8(desc), QT_UTF8(default_path),
 				QT_UTF8(filter));
+	else if (type == OBS_PATH_FILE_SAVE)
+		path = QFileDialog::getSaveFileName(view,
+				QT_UTF8(desc), QT_UTF8(default_path),
+				QT_UTF8(filter));
 
 	if (path.isEmpty())
 		return false;