JUCE major version bump to 3.0.0

With a project like JUCE which moves along by daily incremental changes, it's really difficult to know when to make the call and say "ok, this is now a new version!"

The original v1.0 label stuck around for 10 years until v2.0 came along with the module structure in early 2012, and I think it's now time to make the call and say that things have moved far enough to start calling it a v3.0!

It's been nearly 2 years since v2.0, and there's been a huge amount of progress in that time - loads of new features, and things like the new demo and website which have freshened things up a bit. Also, since I'll soon be adding VST3 support, this seems like a good place to put a milestone.

Important note for commercial licensees!

The number of this version is significant because it's the first one in JUCE history where some of the longer-term license-holders may actually need to.. gasp.. upgrade! The commercial licenses specify (in clause 1.1) how many future versions the license covers, and older licences from 2011 or earler don't reach as far into the future as v3.0.

I've always been pretty generous with these terms, which is why so far I've never had to sell any kind of upgrade, but I don't think it's unfair to finally ask for a little upgrade from those who've been using it for multiple years. It all goes to help fund the next 10 years of development! (and beer). Upgrade forms are available here, and the new version will cover versions 3 & 4.

(Just to clarify: this doesn't affect anyone who's continuing to sell software built with v2.0 - you can keep doing that forever. It's just if you want to start building things with v3.0 code that you'd need to upgrade)