Clarifies differences and similarities in arc and bridge processes
Clarifies comparison between arc and bridge process more

- Stepping stone to see if I can make them more similar
Continues clarification
IMPORTANT clarification of comparison between arcs and bridges

- Changes the understanding of what's going on fundamentally -
talks about higher and lower level items as opposed to what tag
the item has
Break to try negating need for groupG outside updatePart() scope

- Seems to have worked. Keeping console logs in for now.
More notes on comparison of update of arcs vs. bridges
not important, small changes to update procedure comparison
Successfully moves "groupG =" into updatePart()
Note: tried to move newLayout into updatePart(), doesn't work yet
Changes var "newLayoutChord" to "newPartLayout"
Fixes some mistakes in update arcs vs. bridges comparison
Transitions to arc update version detaled at bottom in comments

- Still works. This way will be more clearly organized, especially
when bridge updates work the same way
Comments out weird path id index thing in arcs, still works

- It may have had a function in Sources (3), not sure what it was
though. Should go back and check over how it was used.
- Checked - seems to have been used to as value for the attr
"xlink:href" for group labels. Not sure what function that served
either, doesn't seem to be used anywhere else
Whitespace for compariston of arc vs. bridge
Changes bridge updating to better reflect comments at bottom

- Didn't need much changing, already changed things earlier to
check what worked and what didn't
Removed comments about moving mouseover outside of function

- Reading Source (3)'s comments more closely: this is reset on
every update, so it will use the latest chordPaths selection
This means that it does have to be redone in the function. Not
sure how to keep the queued events from piling up, but it is
necessary and hopefully people will mouse over frequently enough
for it not to be an issue.