MueLu: type issues in LineDetection factory

Created by: lucbv

Bug Report

@trilinos/muelu

Description

The MueLu_LineDetectionFactory is using the type Scalar while manipulating coordinates which creates problems when Scalar=std::complex<>. To fix this the types have been modified to Teuchos::ScalarTraits<Scalar>::coordinateType which ensures that coordinates can be computed on in a sane way.