Rethink decision to use vector arrows.

[brandonLi8]

From #93.

At the recommendation of @pixelzoom:

I'd recommend explaining the problem to your design team, and seeing if you can come up with a design that separates the vector symbols from translated strings.

Here is the problem

The vector symbols for both of the locations will need to be translatable (at the very least the control panel). I anticipate some RTL languages might have the parenthesis before.

So this case is very different from Vector Addition, which uses a scenery Node to place an arrow on top of a single character, and combines multiple Text instances together. This approach wont work for collision lab.

I don't even want to get close to FormulaNode again. See phetsims/scenery#457 (comment).

HTML entities also don't work because they don't work on all platforms, as described in #93.

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I've been thinking about this more, and I'm not quite sure how we arrived at this decision. It seems like phet sims don't traditionally add a symbol in the control panels.

Like for instance, in masses in springs:

or in gravity and orbits:

there isn't a separate label.

One justification for this comes from the design doc:

This will help serve has a key for the Values strings which reference just v & p.

I think that if this was concern, this can be done without the arrow symbol, ie. 'Velocity (v)'.

I agree that the change in momentum checkbox looks uglier

But I think we can change this string to "Change in Momentum"

[arouinfar]

@brandonLi8 thanks for describing the issue. I do not think the abbreviation/vector symbols are necessary, so let's simplify things and go with your last suggestion:

But I think we can change this string to "Change in Momentum"

[brandonLi8]

Thanks @arouinfar. This is done in master. Closing.