We were erroneously using canvas_getrootfor instead of glist_getcanvas to
find the canvas on which the nested gop was being displayed.

Also added a consistency check to turn such a crasher into a runtime bug
in the future.

This was initially part of an effort to prevent double binding to scalars
for certain event callbacks. By unvis'ing all scalars in the graph this
would ensure the symbol would get unbound.

However, we're already doing that in canvas_map. So it appears this extra
unvis'ing in graph_vis was unnecessary.

However, it looks like the scalar in a gop will get unvis'd twice when
destroying the gop canvas. No idea why that is, but if there's a regression
perhaps one of the few people using scalar events will report a regression :)

Proper fix for the nlet highlighting. Now allows for loose aiming and always starts the patch cord at the center of the outlet. Inlets from which we currently cannot connect from are grey when highlighted, while ones you can initiate connection from are orange (both colors are themeable inside the css). Also, if trying to connect an impossible connection (signal to non-signal), when hovering over the non-signal inlet during the connection cycle, such an inlet will be also highlighted gray (grey? whatever...). Lastly, updated the highlighting animation--I am really not particularly interested in animation as it tends to slow down the interaction with the patch, so the animation is much shorter and more minimal. Potential value is leaving it as this to provide visibility of the nlet being highlighted when we are already over it with the cursor, which will otherwise occlude the nlet altogether. Another consideration with the currently committed highlight is that it is hollow inside which looks IMO distracting. Curved edges is also distracting since no other aspect of the UI (save for the customized data structures created by the user) is not curved.

* give new cord the same color as selected line (except for vanilla/ext presets)
* make broken object stand out more
* make comment dash sizes match l2ork 1.0
* change xlet hover animation to match new xlet style

Improved consistent drawing of box sizes between edit and display modes, adjusted positioning of text both in text and graph objects, provided consistent spacing on the left and right sides. TODO: work on auto-updating GOP gray rectangle when its size is adjusted through the sub-patch, as is the case with the 1.x branch.

Fixed bug where GOP patches inside a GOP got highlighted when the parent GOP was selected. By default no subpatches or objects should be visibly highlighted. This should close issue #623.