Add ability for users to block an account/instance on server side

server/controllers/api/accounts.ts

server/controllers/api/search.ts

server/controllers/api/users/index.ts

server/controllers/api/users/me.ts

server/controllers/api/users/my-blocklist.ts

server/controllers/api/video-channel.ts

server/controllers/api/videos/comment.ts

server/controllers/api/videos/index.ts

server/helpers/utils.ts

server/initializers/constants.ts

server/initializers/database.ts

server/lib/blocklist.ts

server/lib/video-comment.ts

server/middlewares/validators/blocklist.ts

server/middlewares/validators/index.ts

server/middlewares/validators/server.ts

server/middlewares/validators/sort.ts

server/models/account/account-blocklist.ts

server/models/server/server-blocklist.ts

server/models/server/server.ts