Redundancy in tmg edge line computation

[yakra]

There's some redundancy writing multi-format edges:

• creating/writing segment name (as needed), between all 3 formats
• iterating intermediate points & formatting strings, between collapsed & traveled

Combine into a single function that sets up the data once, then checks the format mask and writes to one or more files.

• Either use 1 function (or inline it) and use some ifs, or
• Use a function array or switch for formats 1-7, and write what we need where we need it.
  If using a function array, declare the ofstreams an an array & pass a pointer to keep the signature the same.