Grouping headers

[cvvergara]

Changes proposed in this pull request:

• the get_edges et al, that retrieve the postgres information headers are grouped int one file
  • except for arrays_input which lacks of similarity
  • the "reversed" are now done with a flag, reducing the number of get_edges* functions
  • a type was fixed for max cardinality match

@pgRouting/admins

[cvvergara]

will merge when I fix the tests