Change calculation of x-coordinate for new Figure based on average
rather than median of connected figures (command 'p').
Implement hit testing for x values of newly added figures, and change x
to newly added figure to x of hit figure + width of hit figure + 10
Fix calculation of y

- Continue to use (lowestY - _OFFSET_NEWNODE_PARAMETERNODES) for
new parent

- Use (highestY + _OFFSET_NEWNODE_PARAMETERNODES) for new child