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
expose normalizedScale, height, width and add and afterRender listner
return canvas height and width
restore the unnecessary changes
exposing of the normalized scale and afterRender function
expose slice width and hieght
remove redundant code
use default getters
Add after render in 3dRendered also as its called after rendering
Merge pull request #155 from LabShare/enable_tagging

Enable tagging
handle case where n_count = 0 in trk header
Merge branch 'destroyObject' of https://github.com/xtk/X