YT-CPPHGL-12: Implement the bf-directed incidence-list model

[SpectraL519]

1. Created the impl::incidence_list class specialization for the bf-directed model, which:

• Stores an incidence list, where each entry contains separate tail and head collections
• Defines the following operations:
  • Adding and removing vertices
  • Adding and removing hyperedges
  • Binding (tail/head) and unbinding vertices to hyperedges
  • Retrieving the degree, in-degree, out-degree of a vertex
  • Retrieving the set of hyperedges incident with, outgoing from, incoming to a given vertex,
  • Retrieving the number of vertices incident with a given hyperedge and the number of hyperedge's tail/head vertices
  • Retrieving the set of vertices incident with a given hyperedge and the hyperedge's tail/head vertices

2. Added a --clang-format-executable argument to the formatting script

[SpectraL519]

ok