Merge branch 'tetris'

Fix conversion error

Make Entity only movable and provide default behaviour for all functions

Add drawing blending setting to Renderer

Fix small issue

Add virtual size() function to Entity

Add more keys

Add new key_flags

Squash cast warnings

Fix problems with Rect

Add convenience functions for Rect

update SDL and SDL_ttf

Constructors and operators for utl::Rect

Add some default constructors

Add rectangle rendering