Use __init__.py to manage api module

api/__init__.py

@@ -0,0 +1,14 @@
+from api.s0_base import delete_curve, delete_node, delete_pattern
+from project import have_project, create_project, delete_project
+from project import is_project_open, open_project, close_project
+
+from operation import execute_undo as undo
+from operation import execute_redo as redo
+
+from s0_base import add_node, add_link, add_curve, add_pattern
+from s0_base import have_node, have_link, have_curve, have_pattern
+from s0_base import is_junction, is_reservoir, is_tank
+from s0_base import is_pipe, is_pump, is_valve
+from s0_base import delete_node, delete_link, delete_curve, delete_pattern
+
+from s1_title import set_title, get_title