Fix stupid cplex-related bug in primal heuristic

Avoid calling getObjValue() if the status is not (at least)
feasible! Otherwise, cplex will throw an exception and everything
falls apart horribly.
Fix bug when a flow is 0, and print flow in labels
Add option to check a solution file
Add arc formulation to latex notes
Quick fix for final MILP time in output
Create path with correct arc order
Add custom event handler
Print bound changes after node has been processed
Pass mmf arguments to parallel_run.sh or run.sh

Arguments are propagated to mmf.
Also, add option to build a table from arbitrary run,
not only from the last one.
Merge branch 'master' of github.com:sbebo/MMF
Add object for custom branching rule
Add first, naive implementation of branching rule

Branch on an arc constraint; however, it is not working yet.
New pricing variables are not addedto the local constraints!
Build latex automatically
Merge branch 'master' of github.com:sbebo/MMF
Add original arc variables to path formulation

Add arc variables and constraints linking arcs to lambdas.
In pricing and in model construction, add lambdas
to the corresponding arc constraints.

In B&B, use SCIP default branching rules: lambda variables are
now considered continuous, so this should be ok.
However, branching still loops: still something wrong.
Small but important fixes in pricer

In pricer:
- Check equality with SCIPisFeasEQ(). This should prevent numerical
problems (hopefully).
- Check for duplicate paths before adding a new column
- Set lower bound of 1.0 in case arc variable is fixed to 1

In main problem
- Include event handler only if verbosity>=4
Add NDEBUG checks
Add option to (de)activate the extended formulation
Replace all 'string' with NODE
Add name->index lookup table (and viceversa)