wip: add nice object/renderer destructor

done: read the 'reslicing flag' to know if we will reslice the volume or not
done: introduce 2D update() methode, to force an update if the slice has been modified
FIX leak: we were still listening at a request even if it returned:

listen for 'abort', 'failed' and 'load' on the request object
once the request object returns any of them, stop listening for any of them
implement a basic destroy for the volume and slice.

still some leaks to be investigated.
fix compilation warnings
initialize all variables properly in the constructor
fix type mismatch
set minimum height to 1
remove debug log
stop listening to resize events if destroy a renderer
Merge branch 'destroyObject' of https://github.com/xtk/X
fix range error in DCM parsing
fix build error