* Performance/Webpack: Introduces more aggressive code-splitting and other perf improvements
- Introduces dynamic imports for built-in plugins
- Uses dynamic imports for various packages (rst2html, brace)
- Introduces route-based dynamic imports
- Splits angular and moment into separate bundles
Since React and other dependencies bump caused some troubles with building packages that @kaydelaney and me tried to debug without any success, we decided to revert React 16.9.0 bump.
* added new variables for height in theme, added height to gui button large, replaced add gicon with regular gicon, replaced + with gicon, changed button display to flex
* set fixed height to large button, removed xlarge button and replaced with large button
* removed button-mini and replaced with button-small, set fixed height to default button and button-small
* fixed padding for default and large button, fixed height for navbar button, fixed snapshots
* fixed padding and margin on navbar buttons
* gave special height to login btn-primary
* readded btn-mini class with same styling as btn-small and a deprecated notice
* fixed add panel widget buttons
