Zoltan2: Fix scalar type build errors for Ifpack2 using Zoltan2's Scotch ordering (#244)
Created by: MicheldeMessieres
This changes IfPack2 to use RowGraph instead of RowMatrix. Avoids the conflict for the scalar type.
Adds a new adapter for Tpetra::RowGraph. Adds a unit test for that adapter.
We may wish to define the RowGraph type in Ifpack2_AdditiveSchwarz_decl.hpp to parallel RowMatrix though for now I've included it directly in Ifpack2_AdditiveSchwarz_def.hpp for this one-use case.
For Zoltan2 adapters I noticed the unit tests are not verifying that doMigration is properly working but it may be better to fix this as a separate issue. Disabling the doImport calls for example will not cause the various unit tests to fail.