Allow panel/toolbox on right side to expand 50px before scaling down strings

[arouinfar]

Similar to phetsims/masses-and-springs#293

@Denz1994 can you allow the the panels on the right to expand a bit before scaling down the strings? The behavior can match MAS.

Things are looking a bit crowded even for ?stringTest=double

To keep things looking uniform, the gravity accordion box and toolbox should get wider to match the width of the panel above.

[Denz1994]

@arouinfar We adjusted the size of the spring constant panels. Do we still want this pixel expansion, especially on Bounce and Stretch screens?

[arouinfar]

Good point @Denz1994. This request was made before the spring constant panels were widened. Things are currently a bit tight:

Rather than expand the panel, could you extend the maxWidth so the strings get a bit closer to the icon? Currently, there's quite a bit of dead space between the string and icon.

[Denz1994]

The maxWidth has been adjusted to allow for the labels to expand closer to their respective icon. Please review master in MAS and MASB @arouinfar.

[arouinfar]

Looks good @Denz1994!