Updates JUCE to newer version (i.e. v3.0.6)

The JUCE version shipped with OpenEphys is kind of outdated (v2.1.1) and contains major bugs that are already fixed in newer versions (e.g. #142).

Therefore we should update to a newer version of JUCE, at least the v2.1.8 or even v3.0.6. I tested v3.0.6 on OS X and apart from some minor changes I had to make, it builds and runs just fine.

The difference between v2 and v3 seems to be minimal. Sadly I could not really find much information about it and as far as I can tell the switch to v3 was only made, so it would require some of the commercial license customers to renew their license. Therefore this pull request contains all the changes necessary to update JUCE and Introjucer to v3.0.6.