Added All Attribute Type for Vertical Iterator

For both nodes and edges, add each attribute type.
Also, change function declaration so that
vector is pass by reference
Merge branch 'vert_iter' of github.com:snap-stanford/snapr into vert_iter

Conflicts:
	snap-core/graph.cpp
Get rid of ^M Line endings
Merge branch 'vert_iter' into defaults

Conflicts:
	snap-core/graph.cpp