The scene now owns its renderer, so there is no need to keep a list
of existing renderers and to call Renderer::Get().

This was not a very smart class. We replace it with a bidirectional map.

We used to have lol::map::empty() to empty maps, but in std::map
this method is called clear(). It sounds safe to harmonise between
our types and have lol::array::clear() too.

Seems to still build in lol, will check other works to be sure

Added macros to help basic setup

getter default params are better now

Next pass is clean-up and fix of all the old usage

Will resume on other computer.

- removed 0 CR characters
 - removed 7 trailing whitespaces
 - replaced 332 tabs with spaces

- Most recent version is in with index buffer support

This will allow us to generate sounds on the fly on several dedicated
channels. Until now we could only play fully loaded samples.

Input was broken, as well as palette generation, and even texture
upload. Should be all good now.

We have no hope of extending lua_State to add more data to it, because
that object may be created by Lua itself, for instance within a coroutine,
and it has no knowledge of our version of the object.

This will help us deal with shader name collision. Breaks the Windows
build for the moment, unfortunately.

For now the flags are: --disable-doc --disable-test
--disable-samples --disable-tutorial.

All these changes will allow us to more easily add Lol Engine as a
submodule of another Git project.