Support tolerance technique for BellmanFord (#51)

A new operation traits class BellmanFordToleranceOperationTraits
is introduced, which uses the tolerance technique in its less()
function. This class can be used with the SetOperationTraits
named template parameter.

Merge #332

ArgParser can throw exception instead of exit(1) (#332)

Better return type for cycleLength() functions (#179)
in the min mean cycle algorithms.

The original Value type is used instead of the LargeValue type,
which is introduced for internal computations.

Merge 4 backouts (#50, #312)

Back out 4 changesets (#50, #312)
- 532697c9fa53
- bb8c4cd57900
- 9f529abcaebf
- 703ebf476a1d

Merge #340