Gutenberg Demo bits for 11.4

[koke]

Keeping track here of all the things that need to happen for Gutenberg before the 11.4 freeze.

There are a few PRs in Gutenberg that are ready to merge, but the Travis e2e tests are temporarily failing for everyone. Try to restart the builds a few times or get someone with permission to force-merge them.

• Merge Create blocks empty by default gutenberg-mobile#300
• Merge Hide the image upload button on native until it's implemented WordPress/gutenberg#12409, failing e2e tests
• Merge Focus on RichText when selection changes WordPress/gutenberg#12422, failing e2e tests
• Waiting on ☝️, update Gutenberg hash, and merge Focus on RichText when selection changes gutenberg-mobile#298, make sure we're including the changes in Expose focus method react-native-aztec#85
• Implement a way to pass style into Dashicons
• Update Gutenberg in Make block holder and toolbar look nicer gutenberg-mobile#286 and test that the up/down/trash icons in the block toolbar show the right color, and merge
• Merge Show Gutenberg title after it appears #10568 when approved
• Publish a new version of gutenberg-mobile, I think this is worth a --minor bump 😉
• Update Podfile to have Gutenberg point to :tag => 'v0.2.0
• Run bundle exec pod update Gutenberg RNTAztecView, create a PR with the changes, merge
• 🎉 Profit!