show "success" message when activation link is clicked

[davidak]

• Gitea version (or commit ref): 1.1.0+1408-ge87c540a
• Git version:
• Operating system:
• Database (use [x]):
  • PostgreSQL
  • MySQL
  • MSSQL
  • SQLite
• Can you reproduce the bug at https://try.gitea.io: no. i got no mail
  • Yes (provide example URL)
  • No
  • Not relevant
• Log gist:

i used https://staging.teahub.io/

Description

1. create new account
2. click link in e-mail
3. you get to the homepage without any feedback if account activation was successfull