Rename convenience functions in subgraph adaptors (#67)

- Rename hide(), unHide() to disable(), enable().
- Add new set function status(Item, bool).
- Remove hidden() and add status() instead
(which returns the opposite value).

@nodes

label

0

1

2

3

4

5

6

7

8

9

@arcs

		label	capacity

0	1	0	20

0	2	1	0

1	1	2	3

1	2	3	8

1	3	4	8

2	5	5	5

3	2	6	5

3	5	7	5

3	6	8	5

4	3	9	3

5	7	10	3

5	6	11	10

5	8	12	10

6	8	13	8

8	9	14	20

8	1	15	5

9	5	16	5

@attributes

source 1

target 8