Update back-end, free resources on exit, update RNG/fluid

Make general bounding volume (sreBoundingVolume) handling more
complete, with destructor.

Rename a few internal functions, such as InitVertexBuffers (now
called UploadToGPU).

Free almost all data structures upon application exit. Implement
destructors for scene, lights, objects and models. A scene can

Reorganize fluid model as a class derived from srLODModel.

Update random number generator module with current version of
seperate sre-random repository.

Use SRE's random number generator instead of libc in all demos.
be reused or cleared, and uploaded models can optionally be reused.

Update the back-end, add application flags, and allow proper
freeing of resources with sreFinalizeApplication(). Make a proper
distinction between sreRunApplication() (with configurable
initialization flags) and sreMainLoop(), which does not perform
any initialization/finalization.

Signed-off-by: Harm Hanemaaijer <fgenfb@yahoo.com>
Raname sreScene::sceneobject and global_light[]

Rename sreScene::sceneobject and global_light[] to object[]
and light[] (shorted more logical since their presence in
sreScene implies the scene-wide status).

Signed-off-by: Harm Hanemaaijer <fgenfb@yahoo.com>
Update README