Fix additional report issues

[joanagmaia]

Changes proposed ✍️

• Move loading to bottom of widget header to allow interaction if something fails (e.g delete/edit widget)
• Remove "[Identities] Count" from measures
• Add [Sentiment] platform to dimensions when [Sentiment] Average is selected
• Fix graph colors
• Fix chart type pre-selection
• Disable selection components when there is 1 or no options

Relates to #279

Checklist ✅

• Label appropriately with Feature, Enhancement, or Bug.
• Tests are passing.
• New backend functionality has been unit-tested.
• Environment variables have been updated:
  • Local frontend configuration: frontend/.env.dist.local, frontend/.env.dist.composed.
  • Local backend: backend/.env.dist.local, backend/.env.dist.composed.
  • Configuration docs have been updated.
  • Team members only: update environment variables in override, staging and production env. files and trigger update config script.
• API documentation has been updated (if necessary) (see docs on API documentation).
• Quality standards are met.
• All changes have been tested in a staging site.
• All changes are working locally running crowd.dev's Docker local environment.

[joanreyero]

Looks awesome! Thanks for taking care of it so quickly!