Make tokens have displayOptions

[snide]

Summary

Had some time (and felt bad for my lack of help over zoom). Cleaned up the props on the component and made it more flexible. Can discuss if you want a run-thru of the changes.

• There is now a displayOptions prop for setting color, shape, and opaque/solidness (didn't like my name any better than yours!)
• Added two docs examples examples to show how to set custom token displayOptions.
• Properly set up autodocs (I'll show you how this works)

Stuff we should probably do still

• EuiToken should probably have its own docs page and not be on the Icon page (maybe?). The new page should have two examples
  • One showing the default token coloring.
  • One showing the custom token examples
• We might want to consider displaying the token* icons in their own section within the EuiIcon docs page. Right now they're smushed at the end when everything else is alphabetical. It might give us a better chance to explain them.
• Prolly can come up with better naming thatn opaque and tokenTintXX. I didn't have any better ideas but something feels weird. Naming is hard.
• Still a decision with non-"token" icons? Should we allow any icon to be used as I'm doing with the map marker below? If not, we can make some regex to dissallow icons that don't start with token.

[cchaos]

I agree with separating the icons into sections. I've been wanting to do that even with some of the other context specific icons. Also, can the list of named tokens be either alphabetical or something logical like grouping the different shapes together (since they seem to indicate a particular grouping).

[daveyholler]

I agree with these changes. I'll pull it down and have a further look. Thanks for all the help on this.

Regarding the docs, I think separating the tokens into their own section is a solid idea.