don't set redux project title directly from sb uploader; only extract title from .sb2 and .sb3 filenames

load new project, both json and title; set title on file load; draft of code to fetch title from api

* added account navigation menu, copied and adapted from www

* fixed css

* support for login menu, registration menu from www

* Dropdown replaced with MenuBarMenu, override www css in menus

* render and style login dropdown via function from www

* moved menu styling from menu itself to menu bar

* refactoring menu components and containers

* refactor and restyle account nav menu

* cleaned up cruft and css per rschamp's review of PR 3070

styling for title field; correct input target in tests; make download filename safer with default, max length; in playground index, correctly pass props through to gui container

Removing this was the point of moving the test up one level. Thanks @chrisgarrity, good catch!

If the VM is ever instantiated, which happens whenever GUI is instantiated due to default props, then IE11 will crash

* Don't show intro modal if hideIntro passed to PreviewModal

* Add hideIntro prop to GUI

* Move intro modal hiding logic into its own function

And implement toggle on player playground

I don't love this solution, but I remember not being able to figure out a way to not specify the max width because it is needed in order for the flowing to work. Without the max-width, the sprite tiles try to be in a row, pushing over everything else.

Also remove some obsolete code

Pass a `stageSize` property down from a centralized `MediaQuery` in the
GUI component, and control the size of the stage and all surrounding
elements based on that value. Note that this is a pure property and is
not stored in the Redux state, since we gain access to the results of
the media query during `render()` and we shouldn't change Redux state
during `render()`.

Some stage-adjacent elements don't yet react correctly to the smallest
stage size.

There will probably need to be more backpack config options in the future, so just make this a bit more future proof

* Player mode

Add isPlayerOnly property on GUI. Move isFullScreen into mode reducer with isPlayerOnly.

Full screen needs to be a separate prop so that GUI knows what to show when exiting full-screen (either player-only or full editor).

- set `gui-body * {box-sizing: border-box;}` instead of expecting it to be set by the enclosing component/playground, and removed uses of content-box (adjusting sizes as needed) 
- Added `!isPlayerOnly` to the conditions for draggable sprites
- rewrote player example to use player mode.