Castle Game Engine 5.1.2 release (fixes to TCastleControl, tutorial, more)

Castle Game Engine version 5.1.2 was just released! This release brings a couple of fixes and improvements to the engine.

1. New useful events are published on TCastleControl:

   OnOpen: TNotifyEvent
   OnClose: TNotifyEvent
   OnBeforeRender: TNotifyEvent
   OnRender: TNotifyEvent
   OnResize: TNotifyEvent
   OnPress: TControlInputPressReleaseEvent
   OnRelease: TControlInputPressReleaseEvent
   OnMotion: TControlInputMotionEvent
   OnUpdate: TNotifyEvent
   

   These should be used to watch open/close of context, to watch key/mouse events and to perform continuous updates. For detailed documentation of them, see TCastleControlCustom reference.

   Some previously published stuff on TCastleControl is deprecated now and will be removed in next release (sorry, we have to break compatibility — this old stuff really doesn't make much sense, all new code should use new events). Also, the deprecated OnPaint was fixed — just in case you're using it (but please switch to using OnRender soon!).

2. The beginning of the tutorial was much streamlined. We fixed some wording, removed a lot of useless info, and made the beginning of the tutorial really smooth. Now, you really quickly get to the "I made a 3D game!" stage :)

   Also, the tutorial chapter "Adding a simple moving object" was added.

3. Also, as you probably see, the website got a total facelift, using HTML5 and Bootstrap style. Various pages and menus were rearranged to be more helpful. I hope you enjoy the new website — please leave a note in the comments :)
4. You can save almost 0.7 MB from exe size by undefining CASTLE_EMBED_ALL_3D_FONT_VARIATIONS in some cases, see src/base/castleconf.inc for comments.
5. Various testsuite fixes and improvements.
6. Improve CastleCurves API, and also mark most of it as deprecated.