Archived labels

Description

The ability to hide a label when you do not use it very often. An example would be for a milestone or release where a customer does a release quarterly and labels the release Q3-17. When that release is done, they do not want to have the Q3-17 label keep coming up as a choice for a label. However, they want to keep the label for historical perspective and to search on it later. Thoughts @victorwu ?

Proposal

Links / references

See designs