Remove dead or stale code

[vincent-octo]

I think it would be good to:

• Remove commented out code. As it's not clear why it is kept around, and decreases the signal-to-noise ratio (for newcomers to the codebase especially)
• remove old code (the wdl/v2 directory). If there is a need to keep the v2 code alive (for example to compare things), then it should be done by making a git tag instead.

[piotor87]

i agree on point 2. we actually have releases for that