The new behavior is as follows:
IF a user has a token and `features` is not set, we treat it as if the
feature was enabled.
IF a user has a token and `features` is set, we check if the feature
name has a value of "true".
`isJwtFeatureEnabled` also provides a way to specify the default value
in case there is no token.
- add possibility to allow execution of the button's routine besides triggering
`toolbarButtonClicked` API event
- keep backwards compatibility
- get rid of `ToolbarButton`
* feat(toolbox) allow any toolbox button to be displayed as main
fixes the previous behaviour where only a certain set of buttons were whitelisted for being displayed in the main toolbar
* code review
* code review - fix avatar icon position