Third party warnings

This pull silences warnings which come from third party code. For these I tried all sorts of crazy work-arounds to not have to modify the third party code. For the cases where there was no other option, I fell back to adding pragmas to silence the warnings. I figured this was the lesser evil since this doesn't actually modify the code from a running standpoint. See the commit comments for more detailed information. The three problem areas were:

opmapcontrol - needed to add pragmas
qwt - needed to add pragmas
OpenSceneGraph - was able to fix with pragma in our own code

This leaves only a single warning in the codebase which I need help with and have documented in Issue #508. Once that is fixed the warnings work is complete and we can flip all warnings to errors.

@thomasgubler I could use your help double-checking the linux build with OpenSceneGraph. On my box Parallels+Ubuntu+OpenSceneGraph don't get along. So I can't do builds with OSG on Linux (also means TeamCity doesn't cover OSG on Linux). Can you verify that debug and release builds only generate the one Issue #508 warning?