`numberOfTeams` in TeamPolicy related slides

[SteffenSeckler]

In the slides to the current tutorials (e.g., https://github.com/kokkos/kokkos-tutorials/blob/master/Intro-Full/Slides/KokkosTutorial_PACT19.pdf, p. 101ff)
the constructor to TeamPolicy is described as:

TeamPolicy < ExecutionSpace >( numberOfTeams , teamSize )

while on the official kokkos wiki the constructor looks like the following (https://github.com/kokkos/kokkos/wiki/Kokkos::TeamPolicy):

Kokkos::TeamPolicy<>( league_size, team_size [, vector_length])

In my opinion the name numberOfTeams is very misleading, as it appears to be dependent on the teamSize, which it is not. It should be renamed to league_size.

The calculation of work on page 101 might also need an update.