Make it possible to just send new attributes to GUI for [drawpolygon] and friends when a field value changes
(This performs better than erasing and redrawing the scalar in the GUI)

slight change to msg/obj box text y-position to keep hanging letters like "g" from overlapping the xlet

match line-height between svg text and div text

add note in todo about potential loss of data when > 4096 bytes of data
are entered into a message box and sent to Pd

* removed a lot of old, commented tcl code
* remove debugging messages
* remove old commented javascript code

refactor dialog_canvas.html to use javascript objects instead of ["name1", "value1", "name2", "value2", etc.] arrays