PhET-style variable declarations

[jonathanolson]

Declarations of the form:

var a = 5,
  b = 6,
  c = 7;

should be changed to

var a = 5;
var b = 6;
var c = 7;

to match our coding guidelines. It helps to be able to quickly rearrange by swapping lines, delete lines, and add variables faster, and is a bit easier to read.

[jonathanolson]

An example of this is in updateAccelerationVector() in Pendulum.js, but please look for other cases.

[andrey-zelenkov]

Change variable declarations to PhET-style. Reassign to @jonathanolson for verification.

[jonathanolson]

Looks good, thanks!