Refs #8570. Add test for loading vector columns.
Refs #8570. Use rank as well to determine column type in Nexus.
Refs #8570. Add code for saving sizes of rows and tests for it.

We need that information to load the column successfully, we can not
rely on padding values because they might be a part of the vector
stored.
Refs #8570. Add implementation for vector_int column.
Refs #8570. Mode vector column loading code to a function.
Refs #8570. Add support for multiple vector column type loading.
Refs #8570. Rename type parameter to be consistent.