Add additional padding to left of accidentals

[AaronDavidNewman]

I thought it made sense to do the actual formatting changes first, b/c it's hard to evaluate the success of an estimate if there are formatting issues.

This just adds 2 pixels of padding to an accidental block, so they don't get squished against the notes to the left. Also moved a couple of formatting magic numbers to metrics.

Before:

After, 1px padding:

After, 2px padding (this PR):

[sschmidTU]

Nice!
Can the padding be modified though? That would be great. I can see myself prefering only 1 pixel of padding (if at all), to keep scores more compact. Every pixel counts ;)
(also, did you try 1 pixel left padding? wasn't it enough?)

[AaronDavidNewman]

@sschmidTU it is a metric of the font, so I'd image you can override it at a score/application level.
I also included 1 px as a reference.

[0xfe]

Looks good, thanks!