Adding peripheral layout mode.

[num3ric]

I increased the parent view bounds back, just because it shows the different modes and alignments more clearly.

[num3ric]

Ah crap, sorry. I messed up the formatting here :( Let me fix.

[richardeakin]

Understanding the use case here, I'm proposing we add a new Layout subclass, called BoxLayout, that can handle fill and justification of each of its subviews (taking the css box model as a concept guide). Things it would handle:

• justification on both axes (left, right, center, top, bottom)
• fill (percent and pixels)
• padding and margin

Going to leave this open for now..

[num3ric]

Agreed on BoxLayout. We can close this PR.

[richardeakin]

After thinking about this for a while, it is likely to be handy in some cases, even with a BoxLayout for other uses.

I do however think we could use some work on the enum names. For one, I think renaming Mode to Placement would clear things up. Also, I propose that instead of DISTRIBUTE that we call that one CENTERED, and then instead of PERIPHERIAL that we use DIVIDED. Also open to other naming suggestions here.