Improve the Vehicle Routing implementation

[svonolfe]

Some issues and feature requests have been discovered in the VRP 3.4 implementation.

svonolfe:

• the distance matrix is reset when starting an algorithm
• some instances of the LiLim benchmark instances are not named correctly
• vehicles are not assigned correctly when a solution includes empty trips

mkommend:

• the view should be improved to show the parameters of the problem
• the design of the instance interpreters could be improved to avoid code duplication

[svonolfe]

Improved the design of the interpreters so code duplication is avoided in r8649

[svonolfe]

Fixed naming of the LiLim instances in r8650

[svonolfe]

Imrpoved VRP problem instance view in r8651

[svonolfe]

The distance matrix was reset when starting an algorithm the first time (r8652)

[svonolfe]

vehicles were not assigned correctly when a solution includes empty trips (r8653)

[mkommend]

Reviewing comments:

• Use explicit conversions (casts) in Interpreters instead of the as operator.
• IVRPDataInterpreter.GetDataType is not used anywhere.
• Remove the local field distanceMatrix from the VRPProblemInstance and refactor the GetDistance method.

I would suggest that you fix parameters which are determined by the loaded problem instance, e.g. vehicles, depots.

[mkommend]

r8922: Refactored GetDistance method in VRPProblemInstace.

[svonolfe]

r9010: used explicit conversions in Interpreters and removed the unused method IVRPDataInterpreter.GetDataType