Frontend packages/ docker updates

[IsmailM]

• redo packages.json - i.e. remove all unused packages...
• move to yarn v1
  • this will pave the way towards yarn v2/v3 - which are significantly faster
  • there is currently a bug with v2 (That will be fixed in v3) that is stopping us from moving to the parallelised v2.
• Update docker setup for frontend
• move to dart-sass from node-sass - this should use a binary file instead of using libsass
  • had to make changes to scss (change / to math.div() )to allow us to make this change
• Update I18next translation
  • turn off dev mode
  • add browser-side local caching - which will save significant time...

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