Contraction functions based on pgr_contraction

[cvvergara]

New functions to be added

• pgr_contractionDeadEnd
• pgr_contractionLinear

Because those are added change the signature of pgr_contracion

Current signature:

pgr_contraction(Edges SQL, contraction order, [options])
options: [ max_cycles, forbidden_vertices, directed]
Returns set of (type, id, contracted_vertices, source, target, cost)

New signature:

pgr_contraction(Edges SQL,[options])
options: [ directed, methods, cycles, forbidden]
Returns set of (type, id, contracted_vertices, source, target, cost)

Equivalences on options parameter names:
cycles = max_cycles
methods with type INTEGER[ ] with default ARRAY[1,2] = contraction order
forbidden = forbidden_vertices

[cvvergara]

Functions have been created