WIP: refactor and humanize helicopter acceleration

Put a smooth function on top of velocity and
angular velocity for increased usability of
the helicopter mode.
stabilitze navigation against anisotropic screens

Signed-off-by: Simon Thum <simon.thum@igd.fraunhofer.de>
take an offset out of heli navigation input

This intends to increase usability by providing a small no-motion
area for the mouse or finger to rest.

This is highly tailored for our scenes and still needs
some knobs for potential other users!

Signed-off-by: Simon Thum <simon.thum@igd.fraunhofer.de>
Started implementation of a basic ssao shader.
.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	tools/packages.json
Added first SSAO attributes to Scene node;
Cleaned up code.
Cleaned up code and aded documentation for the SSAO methods.
Made SSAO blurring resolution independent and implemented an improvised fix for the depth linearization.
Added vec3 array uniform capability to the shader wrapper.
Cleaned up the SSAO code, added attribute SSAOamount,
fixed artifacts caused by low depth buffer precision,
optimized shaders,
added perspective corrected sampling scheme to SSAO shader.
Merge remote-tracking branch 'upstream/master'
fixed a bug
Added the SSAOblurDepthThreshold attribute.
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'

Conflicts:
	src/Viewarea.js -resolved
Merge pull request #1 from fbrandherm/master

Screen-Space Ambient Occlusion
Merge branch 'master' of https://github.com/x3dom/x3dom into GeoViewpoint_work
Geoviewpoint: added zFar and zNear fields
GeoPositionInterpolator: initial work