Add support for Camera variables

[Pomax]

Added all variables listed on https://docs.flightsimulator.com/html/Programming_Tools/SimVars/Camera_Variables.htm

Fixes #124

[Pomax]

@odwdinc merry christmas, and a happy new year =)

would it be possible to merge this in?

[AntCant]

Thanks @Pomax! Desperately needed the camera state, this works great!

[Pomax]

Cheers. You may want to have a look at #127 too in this case, as I've been adding support for more variables as I run into them being missing (since I'm writing an MSFS demonstrator autopilot in python atm) so if and until the various PRs are merged in, you may want to add git+https://github.com/pomax/python-simconnect@master#egg=simconnect to your requirements.txt (or, of course, a specific commit rather than master)

[Pomax]

superceded by #127