Upgrade to react-toolbox 2.0 beta stream #56
Description
According to the roadmap, react-toolbox 2.0 beta is ready for client apps to use.
It has not been upgraded to eliminate deprecation warnings with React 15.5.x yet (see react-toolbox/react-toolbox#1447 and react-toolbox/react-toolbox#1448). Also, some of its dependencies need to be updated in the same way, such as react-css-themr. There is no open PR for those changes yet. However, the 2.0 stream is likely the only place those issues will be addressed.
The theming is changing quite a bit in 2.0 which results in some issues with the way we're applying the themes. The docs seem to be a mix of 1.x and 2.0 instructions, so it's not yet clear how to do what we need to do. Once the situation is a bit clearer, we can proceed with 2.0.
A better option might be to remove support for react-toolbox altogether. See #87.