Debug draw and erase functionality in new connected front-end

[thaije]

The new HTML frontend has been connected to MATRXS in thenew-frontend branch.
Drawing and erasing works, however a few bugs emerged:

• The draw and erase icons are missing when the icons are pressed top right
• Drawing/erasing does not work when the mousebutton is held down. In that case only 1 tile is selected.
• Draw objects

[wiardjorritsma]

Another bug: draw tool is active by default

[thaije]

To make it able for also drawing over objects, we can do the following:

On every location, there is always a background tile, and potentially a number of objects. Background tiles have a click listener for drawing in the draw mode. Objects have click listeners (right mouse button) for the context menu, and left mouse button for draw in draw mode.

If the user draws over an object, a semi-transparent object is added on top on this location. That object is invisible for mouse clicks, but used as an indication to the user that that location has been selected / drawn (e.g. semi-transparent red). The erase functionality removes this top object again.