Zoltan2: Convert XpetraCrsMatrixAdapter to Tpetra

[cwschilly]

Child issue of #26

• Provide new Zoltan2_TpetraCrsMatrixAdapter that replaces Xpetra one
• Provide meaningful documentation and unit tests for new class

[cwschilly]

@stmcgovern This issue can be closed with #26

[stmcgovern]

thanks @cwschilly