A-Painter on AFrame 1.5 - Various fixes

[Elettrotecnica]

Dear maintainers,

in this pull request I submit to your judgment a few fixes and improvements to a-painter that make it work better on AFrame 1.5.

I could only test these changes on Oculus/Meta devices, but I believe they should not be harmful to other headsets. I am also not sure how to test the exporting of drawings, but I could have a look at that as well with some direction. Saving a drawing and loading it works as well

I have structured the commits so that each one represents a single fix or improvement. Hopefully, this will make reviewing the changes easier.

Short summary of the fixes:

• Replaced deprecated/discontinued idioms from the various threejs reforms
• Replaced old blink control with a fresher one that works
• Fixed various warnings coming from the console

Short summary of improvements:

• computing the start of a stroke does not depend on the controller anymore. Strokes will start at the tip of the brush-tip model, computed dynamically.
• on oculus controllers, the tooltip will dynamically point to the exact button positions, regardless of controller model

[Elettrotecnica]

One additional fix: I have refactored the appearing/disappearing logics of the tooltips so that the lines will also disappear when they fade away.