Move Create bankfull polygon and Create Banklines to the end of Level 2

[mpdougherty]

Banklines are needed to make the cross section site maps meaningful (otherwise you can't see where the edge of water is). The rationale for moving it here is that it is the final step after choosing a bankfull elevation, the goal of Level 2. It was originally placed during the planform steps because it was needed for river planform calculations.