Separated audio cache.
Fixed bug in the audio cache where still used sound might get freed.
Fixes crashes when engine is unloading which were caused
by a race condition between the timer code and engine teardown code.
Since we have everything in samples, and we have 44kHz, we easily
get overflows. Use doubles for calculating the length in
milliseconds more accurately.
Settings works
Help works
Clue database works
Fixed code for inserting objects into scene
Reorganization of few files
Unification & code formatting of few older files
Audio mixer is supporting fading and pan animation
Added support for skipping speech by pressing Return
Added proper support for ambient sounds
Added more code to the dialogue menu
Added tooltips to the Spinner
Fixed calculation of volume and pan of walk steps
Code cleanup & formatting