Issues to apply severity and priority for Plan

Here is a list of issues without severity and priority:

• Introduce colors for epics (and roadmap view in particular) ~"Plan", UX, ~"devops:plan", direction, epics, ~"portfolio management", roadmaps
• Cumulative flow diagram in board GitLab Ultimate, ~"Plan", UX, analytics, boards
• API for filtering epics by open or closed GitLab Ultimate, ~"Plan", api, backend, epics, ~"portfolio management"
• Periodically remove deleted documents from the Elasticsearch index ~"Plan", ~"elasticsearch"
• Epic events in activity feed and cycle analytics ~"Plan", epics, ~"portfolio management"
• Adding issues to epics: the "Add" button improvement. ~"Plan", epics
• Save filter option choice to BE for epics ~"Plan", auto updated, epics
• Error message when entering issue weight value ~"Plan", ~"UX ready", issue weight, issues
• VSM vision visuals for Sep 20th presentation ~"Plan", UX
• Unify path in NamespaceFileUploader with FileUploader & migrate old files ~"Plan", backend, epics, ~"portfolio management"
• Ability to change full name for the service desk user ~"Plan", ~"devops:plan", ~"feature proposal", ~"service desk", settings
• Filtering options for system activity in epics ~"Plan", epics, ~"portfolio management"
• Unauthorized epic participation for groups you are not a member of ~"Plan", ~"bug", ~"devops:plan", epics
• Make GitLab (especially issues) less scary for non-developers ~"Plan", UX, issues
• Benefit-cost score ~"Plan", analytics, epics, issues

/cc @smcgivern