Refactor: make relationships separate from users

haven't yet noticed any obvious downgrades the changes would cause in terms of usability, I can't produce any real UI jumping or added latency anywhere. On the positive note, testing on fosdem.pleroma.lol where relationships aren't provided in statuses everything seems to work correctly. Still need to test all the relationship features more to make sure I'm not missing things

Fixes #819 (closed)

src/modules/users.js

@@ -83,10 +83,6 @@ const unmuteDomain = (store, domain) => {
 }
 
 export const mutations = {
-  setMuted (state, { user: { id }, muted }) {
-    const user = state.usersObject[id]
-    set(user, 'muted', muted)
-  },
   tagUser (state, { user: { id }, tag }) {
     const user = state.usersObject[id]
     const tags = user.tags || []