Emoji v11 and Apple Emoji Update

[xaviershay]

This builds on #146 and makes the following contributions:

• Regenerate JSON files.
• Incorporate short names from Emoji V11.0 and Apple Emoji Update #146 (comment) This is required for the new emoji to flow through to the JSON files.
• Does not output emoji with null categories. This should probably be fixed before merging to a) provide categories for all missing glyphs (only 4: man/woman super hero/villain), since this is a parsing error - they exist in emoji-test.txt, and b) error more loudly if this is detected in the future.

[jwheare]

You can fix the missing categories by changing lines 11/12 of build/data_emoji_names_v11.txt to:

1F9B8{SKIN}-200D-{MALE/FEMALE};{GENDER}_superhero
1F9B9{SKIN}-200D-{MALE/FEMALE};{GENDER}_supervillain

[iamcal]

This PR is looking really good - thank you for all the work you've put into it.

In the changes to build/download_spec_files.sh, please use explicit versions - otherwise the build will immediately break when v12 comes out. Since each new version of Emoji/Uniccode requires a bunch of work to support, this should ne an explicit change.

I can't tell from the GitHub view, but i'll need to rebuild the sheets after merging the PR, ahead of cutting a new release. Rebuilding the JSON sets new grid positions for the emoji, so all sheets needs to be rebuilt, regardless of whether they have updated images. As new images get added for the non-apple sets, they'll need to get rebuilt again. This takes a long time, so maybe i'll spin up some giant EC2 instances to help chew through them.

[xaviershay]

Thank you! I didn't rebuild the sheets. I'm not using that feature so not really familiar with what it is/how it works...