[reports][js] dont let reports be locked with unused exps

Adds a flag to the experiments table to indicate which experiments
need to be added to a group.
Also changes the Lock Button functionality:
- will save report before locking it
- if the report has experiments that aren't in a group,
  the report wont lock and will instead show a modal asking the
  user to either add all exps to a group or remove them.

Closes #529
1 job for 529-unused-exps-in-report in 14 minutes and 40 seconds (queued for 6 seconds)
Status Job ID Name Coverage
  Build
passed #168187
docker-build
build_linux_36

00:14:40

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