Various doc improvements for graph adaptors (#67)

- Add notes about modifying the adapted graphs through adaptors
if it is possible.
- Add notes about the possible conversions between the Node, Arc and
Edge types of the adapted graphs and the adaptors.
- Hide the default values for template parameters (describe them
in the doc instead).
- More precise docs for template parameters.
- More precise docs for member functions.
- Add docs for important public typedefs.
- Unify the docs of the adaptors.
- Add \relates commands for the creator functions.
- Fixes and improvements the module documentation.

@nodes

label

0

1

2

3

4

5

6

7

@arcs

		label capacity

0 	1 	0  	  16

0 	2 	1 	  12

0 	3 	2 	  20

1 	2 	3 	  10

1 	4 	4 	  10

1 	5 	5 	  13

2 	3 	6 	  10

2 	4 	7 	  8

2 	6 	8 	  8

5 	3 	9 	  20

3 	6 	10 	  25

4 	7 	11 	  15

5 	7 	12 	  15

6 	7 	13 	  18

@attributes

source 0

target 7