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.