Repository avatars (#6986)

Repository avatars (#6986)

* Repository avatars

- first variant of code from old work for gogs
- add migration 87
- add new option in app.ini
- add en-US locale string
- add new class in repository.less

* Add changed index.css, remove unused template name

* Update en-us doc about configuration options

* Add comments to new functions, add new option to docker app.ini

* Add comment for lint

* Remove variable, not needed

* Fix formatting

* Update swagger api template

* Check if avatar exists

* Fix avatar link/path checks

* Typo

* TEXT column can't have a default value

* Fixes:

- remove old avatar file on upload
- use ID in name of avatar file - users may upload same files
- add simple tests

* Fix fmt check

* Generate PNG instead of "static" GIF

* More informative comment

* Fix error message

* Update avatar upload checks:

- add file size check
- add new option
- update config docs
- add new string to en-us locale

* Fixes:

- use FileHEader field for check file size
- add new test - upload big image

* Fix formatting

* Update comments

* Update log message

* Removed wrong style - not needed

* Use Sync2 to migrate

* Update repos list view

- bigger avatar
- fix html blocks alignment

* A little adjust avatar size

* Use small icons for explore/repo list

* Use new cool avatar preparation func by @lafriks

* Missing changes for new function

* Remove unused import, move imports

* Missed new option definition in app.ini

Add file size check in user/profile avatar upload

* Use smaller field length for Avatar

* Use session to update repo DB data, update DeleteAvatar - use session too

* Fix err variable definition

* As suggested @lafriks - return as soon as possible, code readability