Override the z-index for the blocks drag layer. At 1000, it will be over everything in the gui other than the navbar itself (monitors on the stage, tutorials, alerts, dropdown menus, etc.)

Fixes useability issue where the drop area was too small, and you couldn't see it.

* Fix all the little RTL layout bugs

- [ ] borders on toolbox and workspace mirror correctly
- [ ] spacing on stage selector is correct
- [ ] stage size icons are mirrored
- [ ] extension library coming soon text is positioned correctly
- [ ] only mirror blocks icon on the tab (others stay right-handed)
- [ ] drop down icon in create variable modal has correct spacing

* FIx RTL backpack header border-radius

* round the bottom corner of paint/sound editors

This makes the editor’s asset panels match the blocks.

- Auditing color CSS and componet CSS to make consistent.
- Made a first pass of changes to increase contrast to elements that previously were problematic

Alphabetize all the things

With jscodeshift thank God

Refactored towards better convention for linting.

* Covers parts of these issues: GUI layout panes (#69), sprite libraries (#12), import buttons (#64), menu bar (#67), and sprite info area (#53)

~ Refactored layout pane structure by removing `display: flex` from `.box`, by default. Declaring flex instead only where specifically needed. This helped fix layout quirks, and should help us avoid hard to find issues related to nested flex boxes

~ Added descriptive classnames to boxes/containers/wrappers. Moved more padding, margins + layout into these wrappers to help with component reusability.

~ Set up a spacer unit variable inside `gui.css`, to start keeping consistent padding, margins and rounded corners between panes. Used [CSS/PostCSS Modules](https://github.com/css-modules/postcss-modules-values) to avoid SCSS dependency.

~ Refactored inline styles from JSX, into CSS files. 2 reasons: a) prepping for reuse of CSS Module variables. b) Feels easier to debug complex flex layouts when all the styles are in one place vs JS/HTML/CSS syntax mixed together

~ Added menu bar into layout via new component, and sprite info header in sprite selector pane, with stubs for the labels + forms. Sprite items are correctly scrolling, while leaving the header fixed, in Chrome. Mostly working in FFx. Not working in Safari, IE yet.

~ Style pass on library modal

~ Experimenting with a few different transition styles: Logo in menu bar, sprite library items, Add buttons.

Move layout styles from component stylesheets to the GUI, or the component that is placing the component.

Add a new `Box` component to control layouts, basically giving a convenient way to lay out with flexbox.

Use `Box` as the output component for any component that may need to be passed layout options. The props passing convention allows giving layout props to the final `Box` component, making wrapping with another `Box` unnecessary in some cases.

The inline css method gives us nothing that CSS modules can't give us. This puts the project more in line with the way www works, and makes CSS actually readable.

Using class names gives us full control of the modal styles.