Traits class + named parameters for MinMeanCycle (#179)

- Add a Traits class defining LargeValue, Tolerance, Path types.
LargeValue is used for internal computations, it is 'long long'
if the length type is integer, otherwise it is 'double'.
- Add named template parameters for LargeValue and Path types.
- Improve numerical stability: remove divisions from the internal
computations. If the arc lengths are integers, then all used
values are integers (except for the cycleMean() query function,
of course).

 prefix=@prefix@

 exec_prefix=@exec_prefix@

 libdir=@libdir@

 includedir=@includedir@

 Name: @PACKAGE_NAME@

 Description: Library for Efficient Modeling and Optimization in Networks

 Version: @PACKAGE_VERSION@

 Libs: -L${libdir} -lemon @GLPK_LIBS@ @CPLEX_LIBS@ @SOPLEX_LIBS@ @CLP_LIBS@ @CBC_LIBS@

 Cflags: -I${includedir}