Does not work yet for the distributed vector...

getConstView should be always used for const operations, because
explicit is better than implicit. Overloading one method for cases which
have a completely different type (ConstViewType is *not* just a
const-qualified ViewType) can be very unclear (or even ambiguous) in
certain cases.

This way we can build with CUDA, Clang and MPI at the same time

unsigned int cannot hold a value of 0.5, it was probably meant to wait
0.5 seconds, i.e. 0.5e6 microseconds.

[ci skip]

The code for explicit template instantiation was already removed anyway...

Also, templates were reordered so that related functions are next to
each other.