Wrapping the movie module

The movie module is very challenging to wrap. In this this issue I enumerate the few details that I still remember and will improve the description/improvements with time.

- First, the commands created by `movie` are in fact executed by the GMT command line (CLI) and because of this they can only operate on files. That is, they cannot operate on variables stored in the memory of a Julia session. This is a limitation that I would like to overcome but ... future work.

- In many cases `movie` runs many processes in the background via system calls to either batch (Win) or bash (Unix) scripts. Some of those cases (that I don't remember right now) are not possible to execute correctly when the process is drive by Julia.

- The GMT.jl has extended GMT in many ways as for example the `contourf` module that in fact is made with internal calls to one or more GMT programs (`grdview` and `grdcontour` in this case). Commands like this one (`contourf`) cannot be used in `movie` because GMT CLI has no idea on what that is.

That said, there are several cases that are already possible to run. A gallery of examples is what is needed. Contributions are very appreciated.