This implementation seemed pretty wrong in multiple ways;
I attempted to fix it (a long time ago) (see diff, you'll see what I'm
talking about), then gave up.
Luckily (?) the code is unused, just sitting there, sad and broken.
Note that this is a major, API-breaking change.
Also bunched into this commit:
- rename namespace `shortestPaths` to `ksp`
- omit unneeded namespace qualifiers
- move tests from `GraphTest` to `KSPTest` and wrote more
- path representation explanation in .md file
Former-commit-id: f395c3df40 [formerly 7fa07d1c8f]
Former-commit-id: f50dd3ce7c