Aquarium fails if webgl2 not available

[GKraats]

Since a short time aquarium totally fails if webgl2 not available.
I am running an old Dell laptop with linux Debian Testing
and firefox, which does not support webgl2.
It only shows a page with misleading errormessage:
"It does not appear your computer supports WebGL"
and loops with varying fps-count.

Problem is caused by recent merge #42.

At aquarium/aquarium-config.js it sets enableVR: true,
causing webgl2 to become the preferred driver.
The first check for driver webgl2 fails, causing the
display of the error-page.
The next check for driver webgl succeeds, causing the
program to continue, but probably because of the active error-page,
it fails displaying the aquarium.

Problem can be solved at tdl/webgl.js at
tdl.webgl.setupWebGL.
Function handleCreationError should only
generate the message but not show it.
The message should be only shown at the end of
tdl.webgl.setupWebGL, if no context is available.

Aquarium is a standard and nice webgl-example, so it should support webgl.
~      

[brianpeiris]

For what it's worth, I did some cursory testing in various browsers and this doesn't seem to break anything.