Setup: Add missing dependencies…

[Ryanf55]

Adds matplotlib, opencv-python and wxPython to all distributions. Works on Linux using a virtual environment. I also converted the requirements from a list to set to prevent duplicates.

Note: There is comment in the source code saying that requiring dependencies breaks things:

# note that we do not include all the real dependencies here (like matplotlib etc)
# as that breaks the pip install. It seems that pip is not smart enough to
# use the system versions of these dependencies, so it tries to download and install
# large numbers of modules like numpy etc which may be already installed

I tried building and installing, and it didn't break my pip install. I used a virtual environment. This comment may no longer be valid.

Solves #1215

[tridge]

this would break the way mavproxy is often installed on headless companion computers. We could add them only on windows though