Optimize image sizes with ImageOptim

Test Plan:
- See images are smaller file size when using image picker in /cs/new/webpage.
Merge pull request #206 from Khan/pf-smaller-imgs

Optimize image sizes with ImageOptim
Update structured-blocks.
Implement click-only number scrubber. Also add in strokeWeight to the toolbox and remove point.
Added comment
Fixes T3422 - imageModal positioning for smaller screens

Summary: The imageModal was getting cut off on smaller screens, so I've made it always be centered for full visibility on the largest range of screen sizes

Test Plan:
- Open imageModal
- Resize window
- See modal stay centered

Reviewers: john, brian, pamela

Reviewed By: pamela

Subscribers: #cs

Differential Revision: https://phabricator.khanacademy.org/D14856
Remove old Bootstrap font stuff that's no longer user.
Integrate new trash drop area and update structured-blocks.
Merge branch 'master' of github.com:Khan/live-editor