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.

prefix=@prefix@

exec_prefix=@exec_prefix@

libdir=@libdir@

includedir=@includedir@

Name: @PACKAGE_NAME@

Description: Library of Efficient Models and Optimization in Networks

Version: @PACKAGE_VERSION@

Libs: -L${libdir} -lemon

Cflags: -I${includedir}